United States v. Weitzenhoff, 35 F.3d 1275 (9th Cir. 1993) is a legal opinion from the Ninth Circuit Court of Appeals that addresses the confusing mens rea requirement of a federal environmental law that imposed criminal sanctions on certain polluters. The main significance of the court's opinion was that it interpreted the word "knowingly" in the statute (that is, a requirement that the violator "knowingly" violated another section of the environmental statute) to mean a general awareness of the wrongfulness of one's actions or the likelihood of illegality, rather than an actual knowledge of the statute being violated. Circuit Court Judge Betty Binns Fletcher authored the majority's legal opinion in this case.