Rule 26.1 United States Federal Rules of Criminal Procedure
Rule 26.1 of the Federal Rules of Criminal Procedure is about Foreign Law Determination. It is under Title VI (Trial) of the Rules.
A party intending to raise an issue of foreign law must provide the court and all parties with reasonable written notice. Issues of foreign law are questions of law, but in deciding such issues a court may consider any relevant material or source—including testimony—without regard to the Federal Rules of Evidence.