What is the current state of the law on the mens rea requirement?

The inclusion of some mens rea requirement is not necessarily enough to ensure that "a broad range of apparently innocent conduct" is not swept into a criminal prohibition. Liparota v. United States , 471 U.S. 419, 426, 105 S.Ct. 2084, 85 L.Ed.2d 434 (1985). If a mens rea requirement is interpreted to require knowledge of only innocent facts, then a person could be convicted despite genuinely believing that his acts were entirely proper. Staples v. United States , 511 U.S. 600, 612, 61819, 114 S.Ct. 1793, 128 L.Ed.2d 608 (1994).