with mens rea :  I would argue that they do.  They are, according to Steven J. Mopsick, the best and brightest lawyers, from the most prestigious institutions.  How could they not know the law?  Their ignorance is thus no excuse. 20 Responses Nice reflection. I have often thought along similar lines but you summed it up. "actus non facit reum, nisi mens sit rea" does this mean that even if one is not ignorant of the law but believes it to be unconstitutional, a violation of local sovereignty and against natural legal principles -- one has no guilty concience and is innocent? I think so in some cases. FBAR FATCA, CUT, and double taxation are some of the manifest ones. Just look at what most Europeans would say when you speak about these laws: "you are crazy, you must pay your taxes here where you live... go get your head checked". I am glad I am relinquishing my US citizenship soon. I thought, they were kidding when I first heard about FBAR and even dual-citizens must file, even if they never visited the USA in decades. My feeling was, only communist countries like North Korea or countries like Saudi Arabia ruled by dictators can have this kind of laws. (I left USA many years ago, I don't know that the US is now ruled by dictator Obama). Also how many of cigar lovers know that it is illegal for US citizens to buy or smoke Cuban cigars, even in the