OPINION

Before CHAMBERS, HUFSTEDLER and WALLACE, Circuit Judges.

Bergstralh seeks to recover damages under section 1983 of the Civil Rights Act, 42 U.S.C. § 1983 , resulting from his arrest on charges of disorderly conduct by Lowe, a policeman employed by the city of Bend, Oregon. Bergstralh summoned Lowe to remove two alleged trespassers from his appliance store parking lot. When Lowe convinced the young men to leave and refused to arrest them, Bergstralh threw some beer bottles and made threatening and abusive remarks to Lowe and the young men. Lowe arrested Bergstralh without a warrant and charged him with disorderly conduct. Bergstralh was subsequently acquitted on that charge by a municipal court, but convicted on a charge of resisting arrest. In the district court, Bergstralh asserted that Lowe violated his Fourth and Fourteenth Amendment rights by using excessive force and illegally arresting him. The district court ruled at the conclusion of Bergstralh’s case-in-chief that, as a matter of law, the arrest was made with probable cause. The question of excessive force was submitted to the jury, which returned a verdict in favor of Lowe. Bergstralh now appeals, urging that the district court erred in its ruling on probable cause and in instructing the jury. We affirm.

Bergstralh’s primary claim is that because probable cause was absent, Lowe deprived him of his constitutional rights by illegally arresting him. The lawfulness of a state arrest by state police is to be determined by state law so long as the state law is not inconsistent with the federal Constitution. Ponce v. Craven, 409 F.2d 621, 625 (9th Cir. 1969). See Van Camp v. Gray, 440 F.2d 777 (10th Cir. 1971). Bergstralh does not argue that the Oregon laws governing arrest, if followed, are unconstitutional. Thus, our only task in this case is to determine if the district court’s ruling on probable cause was proper under Oregon law.

Bergstralh argues that since under Oregon law a police officer can make a warrantless arrest for a misdemeanor only when a crime is attempted or committed in his presence, his acquittal on the disorderly conduct charge by the municipal court conclusively establishes that his arrest was improper and entitles him to a civil judgment. We reject this argument as being without merit. Beauregard v. Wingard, 362 F.2d 901 (9th Cir. 1966). As the Supreme Court said in Pierson v. Ray, 386 U.S. 547, 555 , 87 S.Ct. 1213, 1218 , 18 L.Ed.2d 288 (1967):

During a pretrial conference in chambers, the district court, relying upon Hryciuk v. Robinson, 213 Or. 542 , 326 P.2d 424 (1958), and Restatement of Torts § 667(1) (1938), ruled that Berg-stralh’s conviction for resisting arrest *1278 conclusively established that the arrest was made with probable cause unless Bergstralh could show that his conviction was obtained by fraud, perjury or other corrupt means. When Bergstralh was asked whether he intended to attempt to establish that the conviction fell within one of the exclusions, the proceedings went off the record. Thus, we are unable to determine toward which issues Bergstralh’s evidence was directed.

After Bergstralh had presented his case-in-chief, Lowe moved for a directed verdict. The court denied the motion, but “rule[d] as a matter of law [that] there was probable cause for the arrest.” The court then stated, “I think the only question the Court feels there is any evidence on . . .is whether excessive force was used in placing [Bergstralh] under arrest.” In response to Bergs-tralh’s argument against the ruling, the court stated:

“You are ignoring entirely the evidence by the other witnesses which you called as part of your ease, all of whom said the bottles went out into the street. You have got a conflict certainly that would give the officer probable cause to arrest this man.”

It is unclear to us whether the court’s ruling was based upon Bergstralh’s failure to rebut the presumption adopted during the pretrial conference or upon all of the evidence presented during the case-in-chief. Clearly, the presumption was not rebutted and, therefore, any alternative holding would be unnecessary and thus any error in ruling on the alternative ground would be harmless.

Whether a rebuttable presumption should be applied is a matter of substantial law. Cf. Blue Diamond Coal Co. v. United Mine Workers, 436 F.2d 551 (6th Cir.), cert. denied, 402 U.S. 930 , 91 S.Ct. 1525 , 28 L.Ed.2d 863 (1970); Peterson v. Mountain States Telephone & Telegraph Co., 349 F.2d 934 (9th Cir. 1965). Accordingly, we are required to apply the Oregon presumption when testing the legality of an Oregon arrest, unless such an application would be inconsistent with the Constitution. Dick v. New York Life Ins. Co., 359 U.S. 437 , 79 S.Ct. 921 , 3 L.Ed.2d 935 (1959). Although Hryciuk v. Robinson, 213 Or. 542 , 326 P.2d 424 (1958), and the Restatement of Torts both deal with a presumption for probable cause in a malicious prosecution by a private citizen, not probable cause for arrest by a police officer, the Hryciuk presumption as applied in this case does not deprive Bergstralh of his constitutional rights. The trial judge concluded that the municipal court jury in reaching a verdict of guilty for resisting arrest would have had to have concluded that Lowe had probable cause to believe that a misdemeanor was being committed in his presence. He was correct. As there was no statute to the contrary, 1 Bergstralh was entitled to use all force reasonably necessary to resist an unlawful arrest. United States v. Di Re, 332 U.S. 581, 594 , 68 S.Ct. 222 , 92 L.Ed. 210 (1948) ; Basista v. Weir, 340 F.2d 74 (3d Cir. 1964). Thus, in order to conclude that Bergstralh was guilty of resisting arrest, the jury would have had to have concluded that his arrest was legal. Absent probable cause the arrest could not have been legal; thus, the issue was directly resolved by the jury. Since this issue had been resolved against Bergstralh by a jury, it was not error for the trial judge to conclude as a matter of law that there was probable cause, unless Bergstralh could show that the jury verdict was obtained by fraud *1279 or perjury. Bergstralh has not succeeded in so showing.

As to instructions, we cannot review Bergstralh’s claim that the district court erred in failing to instruct the jury that the acts of the three men who assisted Lowe in arresting Bergstralh should be considered in determining whether the force used was reasonable and in failing to instruct the jury that taking Bergstralh to jail was not a necessary element of the arrest. Bergstralh did not specifically assert these errors in the district court proceedings. See Fed.R.Civ.P. 51; Sears v. Southern Pacific Co., 313 F.2d 498, 505 (9th Cir. 1963).

Bergstralh’s remaining allegations of error are without merit. The court did not err in refusing to give a specific instruction that, in some circumstances, no force at all is necessary for an arrest since its instruction on reasonable force was sufficient to alert the jury to that possibility. The court also did not err in instructing the jury that reasonable force is determined by what force Lowe believed was necessary because the court expressly stated that the test was whether that belief was reasonable under the circumstances. The court adequately distinguished between Lowe’s belief and whether that belief was reasonable.

Affirmed.

. In 1971 (subsequent to this case), a statute was adopted which prohibited the use of physical force to resist an arrest when the person has reasonable cause to believe that the arrest is being made by a police officer, whether the arrest is lawful or unlawful. ORS § 161.260 (1971). At the same time, a statute was also adopted which provided that it is not a defense to a crime of resisting arrest that the i>eace officer lacked legal authority to make the arrest. ORS § 162.-315 (1971). Under the present Oregon Laws, a conviction for resisting arrest would, of course, not be evidence of probable cause for the arrest.