OPINION

Sandoval was convicted of delivery of a controlled substance under Oregon Revised Statutes § 475.992(l)(a). 1 Oregon law permits conviction for delivery under this statute based on mere solicitation. Because the Controlled Substances Act does not punish soliciting delivery of controlled substances, § 475.992(l)(a) cannot be a categorical match to an aggravated felony under 8 U.S.C. § 1227 (a)(2)(A)(iii). Further, because § 475.992(l)(a) is indivisible, the modified categorical approach does not apply. Therefore, we grant Sandoval’s petition and remand for further proceedings.

I

Leonel Sandoval moved to the United States from Mexico when he was nine years old. He adjusted to lawful permanent resident status in 1990. His wife of over 26 years and two children are United States citizens.

In 1998, Sandoval was convicted of delivery of a controlled substance under Oregon law. The indictment identified the controlled substance as heroin. He performed community service at a forest project and was placed on probation for two years. Since then, he has not been convicted of any other criminal activity. 2

Twelve years later, the government instituted removal proceedings against him. It alleged two grounds for removal based on Sandoval’s 1998 conviction: (1) that the conviction was an aggravated felony and (2) that the conviction was related to a controlled substance. See 8 U.S.C. § 1227 (a)(2)(A)(iii), (B)(i). Under the second charge, Sandoval could seek cancellation of removal based on his long-standing residence and family ties in the United States. But the first charge made him ineligible for such relief. See id. § 1229b(a)(3). Accordingly, Sandoval argued the government had failed to offer clear and convincing evidence he was convicted of an aggravated felony because Oregon’s statute is broader than a federal controlled substance offense given that it punishes solicitation in addition to actual and attempted delivery. The IJ and BIA rejected this argument, concluded he was ineligible for cancellation of removal and ordered him removed.

Sandoval timely petitioned for review. We have jurisdiction and review Sandoval’s petition de novo. See 8 U.S.C. § 1252 (a)(2)(D); Daas v. Holder, 620 F.3d 1050, 1053 (9th Cir. 2010); see also Coronado-Durazo v. INS, 123 F.3d 1322, 1324 (9th Cir. 1997). We do not defer to an agency’s intérpretations of state law or provisions of the federal criminal code. See Hoang v. Holder, 641 F.3d 1157, 1161 (9th Cir. 2011).

II

To determine whether a state criminal conviction is an aggravated felony, we must follow the “categorical approach.” See Descamps v. United States, — U.S. —, 133 S.Ct. 2276, 2281 , 186 L.Ed.2d 438 (2013). Under the categorical approach, we “compare the elements of the statute forming the basis of the [petitioner’s] conviction with the elements of the ‘generic’ crime— ie., the offense as commonly understood.” Id. Only if the elements in the petitioner’s statute of conviction “are the same as, or narrower than, those of the generic offense” is the petitioner’s conviction a categorical match. Id.

*989 Under the categorical approach, we first determine the definition of the generic offense—here, an aggravated felony. This requires us to navigate a “maze of statutory cross-references.” Carachuri-Rosendo v. Holder, 560 U.S. 563, 567 , 130 S.Ct. 2577 , 177 L.Ed.2d 68 (2010). We start with the definition of “aggravated felony” as used in 8 U.S.C. § 1101 (a)(43).

The term “aggravated felony” includes any “drug trafficking crime.” 3 8 U.S.C. § 1101 (a)(43)(B). Only felonies qualify as “drug trafficking crime[s].” See Lopez v. Gonzales, 549 U.S. 47, 55, 60 , 127 S.Ct. 625 , 166 L.Ed.2d 462 (2006); see also Carachuri-Rosendo, 560 U.S. at 581-82 , 130 S.Ct. 2577 . A “felony” means an offense punishable by more than one year under federal law. See 18 U.S.C. § 3559 (a)(5); see also Moncrieffe v. Holder, 569 U.S. 184 , 133 S.Ct. 1678, 1683 , 185 L.Ed.2d 727 (2013); Lopez, 549 U.S. at 60 , 127 S.Ct. 625 (“In sum, we hold that a state offense constitutes a ‘felony punishable under the Controlled Substances Act’ only if it proscribes conduct punishable as a felony under that federal law.”). 4

Drug trafficking crimes include felonies punishable under the Controlled Substances Act. See 8 U.S.C. § 1101 (a)(43)(B); 18 U.S.C. § 924 (c)(2). Because heroin is a federally controlled substance, see 8 U.S.C. § 1101 (a)(43)(B); 21. U.S.C. §§ 802(6), 812(c)(sched. I)(b)(10), knowingly distributing or possessing with intent to distribute heroin violates the Controlled Substances Act, see 21 U.S.C. § 841 (a)(1). Doing so is a felony, i.e., a crime punishable by more than one year of imprisonment under federal law. See 21 U.S.C. § 841 (b)(1)(C). Ae-cordingly, because distributing heroin is a drug trafficking crime, we must consider the meaning of “distribute.”

The term “distribute” means “deliver.” See 21 U.S.C. § 802 (11). And “deliver” means “the actual, constructive, or attempted transfer of a controlled substance or a listed chemical, whether or not there exists an agency relationship.” Id. § 802(8).' Accordingly, one may commit a drug trafficking crime by actually delivering, attempting to deliver or possessing with intent to deliver heroin.

Because Sandoval argues the Oregon statute under which he was convicted criminalizes solicitation, we must next determine whether the meaning of “attempt” under the Controlled Substances Act includes solicitation. The Controlled Substances Act does not define the term “attempt.” See 21 U.S.C. §§ 802 , 846. Nevertheless, mere solicitation of controlled substances does not constitute “attempted” delivery under the Controlled Substances Act. See United States v. Rivera-Sanchez, 247 F.3d 905, 908-09 (9th Cir. 2001) (en banc), superseded on other grounds as stated in Guerrero-Silva v. Holder, 599 F.3d 1090, 1092 (9th Cir. 2010); see also Leyva-Licea v. INS, 187 F.3d 1147, 1150 (9th Cir. 1999); Coronado-Durazo, 123 F.3d at 1325-26 . The Controlled Substances Act “does not mention solicitation,” unlike “attempt” and “conspiracy.” Rivera-Sanchez, 247 F.3d at 909 (quoting Leyva-Licea, 187 F.3d at 1150 ); see also Coronado-Durazo, 123 F.3d at 1325 ; 21 U.S.C. § 846 (prescribing felony punishment for attempting or conspiring *990 to deliver a controlled substance). Although strongly corroborative of intent to commit a crime, offering to deliver a controlled substance does not cross the line between preparation and attempt for the purposes of the Controlled Substances Act. See Rivera-Sanchez, 247 F.3d at 908-09 ; see also United States v. Yossunthorn, 167 F.3d 1267, 1272-73 (9th Cir. 1999) (ordering drugs from a known supplier was. not an attempt when, there was no agreement as to essential details regarding the transaction).

Therefore, to qualify as an aggravated felony, a drug trafficking crime for delivery of heroin must satisfy 'the following elements: (1) knowing or intentional (2) delivery, attempted delivery, conspiracy to deliver or possession with intent to deliver (3) heroin. This offense may not be accomplished by merely soliciting delivery—i.e., offering delivery—of heroin. The next question is whether Sandoval’s Oregon statute of conviction matches this federal definition!

Sandoval was convicted of delivering a controlled substance. His indictment identifies the controlled substance as heroin and cites Oregon Revised Statutes § 475.992. The only portion of that statute proscribing delivery of heroin, states:

Or. Rev. Stat. § 475.992 (l)(a) (1998). .The term “deliver” means “the actual, constructive or attempted transfer” of a controlled substance from one person to another. Id. § 475.005(8) (1998). “A person is guilty of an attempt to commit a crime when the' person intentionally engages in conduct which constitutes a substantial step toward commission of the crime.” Id. § 161.405(1) (1998).

Under Oregon law, solicitation— even without possession—is a “substantial step toward committing the crime of attempted delivery under ORS 475.992(1).” State v. Sargent, 110 Or.App. 194 , 822 P.2d 726, 728 (1991); see also State v. Lawrence, 231 Or.App. 1 , 217 P.3d 1084, 1086 (2009). And, taking a substantial step toward committing the crime of attempted delivery by solicitation “constitutes delivery” in Oregon. Sargent, 822 P.2d at 728 .

Sargent relied on State v. Self, 75 Or.App. 230 , 706 P.2d 975 (1985), in concluding that mere solicitation supported a conviction for delivery of controlled substances under § 475.992(l)(a). See Sargent, 822 P.2d at 728 . In Self , the defendant was convicted under Oregon’s generic solicitation statute, Oregon Revised Statutes § 161.435. See 706 P.2d at 977 . The court set out the specific facts:

Id. Self was convicted of “solicitation of attempted delivery of an illegal substance.” Id. The appellate court affirmed. See id.

That the appellate court in Sargent said the facts of Self were “illustrative” is telling. See Sargent, 822 F.2d at 728. Self did not possess or even offer to deliver the *991 cocaine. See Self, 706 P.2d at 977 . Instead, he tried to arrange the release of a third party, promising that same third party would obtain cocaine in exchange for assistance in the third party’s release. See id. There was no agreement to accomplish this scheme. See id. Further, the court recited no facts indicating the third party’s willingness to perform the promised criminal acts. See id. Nevertheless, the appellate court in Sargent pointed to Self as the “illustrative” case supporting its conclusion that “delivery” under § 475.992(l)(a) includes solicitation. Sargent, 822 P.2d at 728 . This holding has not been disturbed by later Oregon case law.

For example, in State v. Pollock, 189 Or.App. 38 , 73 P.3d 297 (2003), aff'd on other grounds, 337 Or. 618 , 102 P.3d 684 (2004) the court reversed a pretrial order suppressing evidence against a defendant charged under § 476.992 for delivery of a controlled substance. In Pollock , an officer had been told by witnesses that the defendant had tried to sell them ecstasy, a controlled substance. See id. at 298. The trial court found that “an offer to sell a controlled substance is, standing alone, insufficient to establish. probable , cause to believe that an attempted transfer has occurred.” Id. at 299. The appellate court reversed:

Id. at 300 (alterations in original) (emphases added). Thus, under Oregon law, the offer to deliver a controlled substance is enough to complete a substantial step toward an intended transfer, ie., offering to deliver a controlled substance is an attempt under Oregon law. See id. But the mere offer to deliver a controlled sub stance—ie., the act of soliciting delivery— is not a drug trafficking crime under the Controlled Substances Act. See Rivera-Sanchez, 247 F.3d at 908-09 . Accordingly, a statute that punishes the mere offer to deliver a controlled substance is not an aggravated felony under the categorical approach. See id. at 909 .

The government contends a conviction under § 475.992(l)(a) requires more than simply offering to deliver a controlled substance. It relies on State v. Johnson, 202 Or.App. 478 , 123 P.3d 304 (2005). We are not persuaded.

In Johnson , the defendant was convicted of both attempted murder and solicitation to commit murder. See id. at 306. During phone' conversations and in online chats, the defendant asked a friend to kill both *992 his wife and daughter, suggesting methods for the murders and offering to make sure the friend would “never want for anything” if she did as asked. See id. Because the state had no evidence of a “concrete” plan outlined for the murder of his wife and child, the defendant argued the evidence was insufficient to support a solicitation or attempt conviction. See id. at 307-08. The appellate court disagreed and affirmed his conviction on appeal. See id. at 310. The government contends Johnson stands,for the proposition that mere solicitation'— simply offering to deliver a controlled substance—is not enough to convict under § 475.992(l)(a). We do not read it.that broadly.

First, Johnson did not involve a controlled substance offense under Oregon law. See id, at 305. Instead, it dealt with attempted murder and solicitation to commit murder. See id. at 306. 5 Thus, it is not clear whether Johnson is applicable here.

Second, even if Johnson is applicable, the standards, the court outlined match those in Sargent :

Id. at 309-10 (footnotes omitted). The appellate court’s reasoning in Johnson was that solicitation is both strong evidence of criminal purpose and a substantial step toward accomplishing that purpose under Sargent. See id. Nothing in Johnson requires a defendant to take some affirmative act to further the goal of the requested criminal behavior or specify how the crime would take place. See id.. at 308 (“[The] details of how the crime is to be committed need not be specified.”). 6 Johnson does not limit Sargent in any way.

In sum, the government’s argument fails to acknowledge Sargent’s and Pollock’s explicit statements that a conviction under § 475.992(l)(a) may be supported by merely offering to deliver controlled substances. See Sargent, 822 P.2d at 728 (“We conclude that, if a person- solicits- another to engage in conduct constituting an element of the crime of delivery ..., the person has taken a substantial step toward committing the crime of attempted delivery ,.. [and] [u]nder that statute, the conduct constitutes delivery.”); Pollock, 73 P.3d at 300 (“We conclude that offering to sell a controlled substance constitutes a substantial step toward a completed transfer of that substance.”). As we have repeatedly held, solicitation of controlled substances is not an aggravated’ felony under the Con *993 trolled Substances Act. See, e.g., Rivera-Sanchez, 247 F.3d at 909 .

Because Oregon’s definition of “delivery” includes solicitation, § 475.992(l)(a) is not a categorical match to a “drug trafficking crime.” Therefore, Sandoval’s conviction for delivery of heroin does not qualify as an aggravated felony under the categorical approach.

Ill

Our inquiry does not end here, however. We must next address whether the modified categorical approach may be used to determine whether Sandoval’s conviction qualifies as an aggravated felony.

Only divisible statutes are subject to the modified categorical approach. See Lopez-Valencia v. Lynch, 798 F.3d 863, 867-69 (9th Cir. 2015) (holding Descamps divisibility analysis is applicable in the immigration context). “[Djivisibility hinges on whether the jury must unanimously agree on the fact critical to the federal statute.” Id. at 868-69 . Such critical facts are “elements,” which are the “things the ‘prosecution must prove to sustain a conviction.’ ” Mathis v. United States, — U.S. —, 136 S.Ct. 2243, 2248 , 195 L.Ed.2d 604 (2016) (quoting Black’s Law Dictionary 634 (10th ed. 2014)).

To resolve the question of whether statutory alternatives are either elements or means, a court looks first to the statute itself and then to the ease law interpreting it. See id. at 2256-57 ; see also Almanza-Arenas v. Lynch, 815 F.3d 469, 479-82 (9th Cir. 2016) (en banc). If state law fails to answer the question, a court may look to Shepard documents, which may be helpful in determining divisibility. See Mathis, 136 S.Ct. at 2256-57 ; see also Descamps, 133 S.Ct. at 2284 (citing Shepard v. United States, 544 U.S. 13, 25-26 , 125 S.Ct. 1254 , 161 L.Ed.2d 205 (2005)). But if the statute, case law and Shepard documents fail to speak plainly as to whether statutory alternatives are elements instead of means, the statute is indivisible and the modified categorical approach has no application. See Mathis, 136 S.Ct. at 2257 ; see also In re Chairez-Castrejon, 26 I. & N. Dec. 819, 819-20 (BIA 2016) (holding Descamps and Mathis divisibility analysis “applies in immigration proceedings nationwide to the same extent that it applies in criminal sentencing proceedings”).

The government does not argue § 475.992(l)(a) is divisible. Instead, it urges us to remand to the BIA to determine'whether § 475.992 is divisible. When an agency does not reach an issue for which it is owed Chevron deference, “the proper course, except in rare circumstances, is to remand to the agency for additional investigation or explanation.” INS v. Ventura, 537 U.S. 12, 16 , 123 S.Ct. 353 , 154 L.Ed.2d 272 (2002) (internal quotation marks omitted); see also Gonzales v. Thomas, 547 U.S. 183, 186 , 126 S.Ct. 1613 , 164 L.Ed.2d 358 (2006). But interpreting criminal law is not a matter placed primarily in agency hands. See Hoang, 641 F.3d at 1161 . We owe no' deference to the decision of the BIA on this issue and there is no reason to remand for thé BIA to decide the issue of divisibility in the first instance. See Rivera v. Lynch, 816 F.3d 1064 , 1078 n.13 (9th Cir. 2016) (“The question of [a state criminal statute’s] divisibility ‘requires neither factual development nor agency expertise’ and is properly analyzed by this court.” (quoting Chavez-Solis v. Lynch, 803 F.3d 1004 , 1012 n.6 (9th Cir. 2015))).

Section 475.992(l)(a) does not list “solicitation” as an alternative method of accomplishing delivery. Nor is solicitation included in the express statutory definition of “deliver.” See id. § 475.005(8). The inclusion of solicitation as a means of accomplishing delivery is a judicial interpretation of the word “attempt.” Therefore, this is a *994 circumstance where the divisibility analysis is “straightforward” ■ because § 475.992(l)(a) “sets out a single (or ‘indivisible’) set of elements to define a single, crime.” Mathis, 136 S.Ct. at 2248 . Solicitation is not an enumerated statutory alternative to delivery or attempt but is, instead, included within the meaning of those listed alternatives. See Sargent, 822 P.2d at 728 . The statute is therefore indivisible with respect to whether an “attempt” is accomplished by solicitation.

The government argues we have previously held § 475.992(l)(a) could qualify as an aggravated felony under the modified categorical approach, citing United States v. Chavaria-Angel, 323 F.3d 1172, 1177-78 (9th Cir. 2003). In that ease, we affirmed the district court’s conclusion that the defendant’s § 475.992 offense for delivery of a controlled substance was an aggravated felony based on a review of uncertified Oregon state records. See. id. at 1174, 1177-78. However, the decision rested on the method rejected in Descamps, 133 S.Ct. at 2282-83, 2286-91 , and applied the modified categorical approach without performing any divisibility analysis. See Chavaria-Angel, 323 F.3d at 1177-78 . The analysis improperly focused on what the defendant' actually did as opposed to the crime of which the defendant was convicted. Compare id. (focusing on the evidence supporting a finding the defendant sold controlled _ substances), with Descamps, 133 S.Ct. at 2287 (calling this method a “modified factual” approach, which''turns an “elements-based inquiry into an evidence-based one”). The opinion did not consider whether a jury, when convicting a defendant of delivery of a controlled substance, must unanimously choose between alternative methods of delivery, including solicitation. See Chavaria-Angel, 323 F.3d at 1177-78 . Descamps and Mathis require these inquiries. See Mathis, 136 S.Ct. at 2256-57 ; Descamps, 133 S.Ct. at 2286-91 . Chavaria-Angel , therefore, is not controlling here.

To summarize, § 475.992(l)(a) is over-broad in its definition of “delivery,” and the modified categorical approach may not be applied because § 475.992(l)(a) is indivisible with respect to whether an “attempt” ' is accomplished by solicitation. Therefore, we hold a conviction for delivering heroin under § 475.992(l)(a) is not an aggravated felony. Sandoval’s petition is granted.

GRANTED AND REMANDED.

. Section 475.992(l)(a) is currently codified at Oregon Revised Statutes'§ 475.752.

. Sandoval was recently pardoned for his conviction, but we do not consider whether or how the pardon affects Sandoval’s ability to obtain relief from deportation.

. The previously published version of this opinion also considered whether § 475.992(l)(a) was an "illicit trafficking” offense under 8 U.S.C. § 1101 (a)(43)(B), which is also an aggravated felony. See Sandoval v. Yates, 847 F.3d 697, 699, 701 (9th Cir. 2017). Because the BIA did not consider this issue, we decline to do so here.

. The Controlled Substances Act defines "felony” as "any Federal or State offense classified by applicable Federal or State law as a felony.” 21 U.S.C. § 802 (13). But 18 U.S.C. § 3559 (a) controls for immigration purposes. See Moncrieffe, 133 S.Ct. at 1683 ; see also Carachuri-Rosendo, 560 U.S. at 567 , 130 S.Ct. 2577 .

. We do not consider whether solicitation to commit murder is an aggravated felony,

. This was exemplified in State ex rel. Juvenile Department of Union County v. Krieger, 177 Or.App. 156 , 33 P.3d 351, 352 (2001), in which the Oregon appellate court affirmed "without discussion” a conviction for solicitation. There, a minor asked several students to help him "blow up or shoot up" their school. See id. All of these requests were rejected and the minor "never pursued any further discussion" or provided "specific plans to carry out the shooting or bombing.” Id. Nevertheless, the minor's conviction for solicitation was summarily affirmed by the court. See id.