As told to the WSJ (and I realize it’s not all a quote; bear with me):
The growing number of federal laws with weakened mens rea safeguards is making the venerable legal principle that ignorance of the law is no defense a much riskier proposition for people. That principle made sense, says University of Virginia law professor Anne Coughlin, when there were fewer criminal laws, like murder, and most people could be expected to know them.
But when legislators “criminalize everything under the sun,” Ms. Coughlin says, it’s unrealistic to expect citizens to be fully informed about the penal code.” With reduced intent requirements “suddenly it opens a whole lot of people to being potential violators.” [emphasis added]
In my rant from earlier this year on no-knock warrants, I mentioned this; I think it bears repeating.
Title 18 of the US Code is made of 2725 sections, and every damn one of them is criminal/penal related.
Ignorance of the law, at this point, is rational.