In the wake of media reports that 40,000 new federal, state, and local laws will go into effect this year, there’s no better time for Americans to revisit the old maxim that “ignorance of the law is no excuse.” An unknown number of these new provisions are criminal laws that can deprive us of our liberty and brand us for life. No ordinary American can be expected to know every law, new and old, on the books, not even every criminal law. Anyone concerned about Americans’ being locked up for innocent behavior should resolve to help end overcriminalization.

Overcriminalization strikes at the heart of our constitutional order. In Bouie v. City of Columbia the U.S. Supreme Court explained the constitutional doctrine of “fair notice,” which holds that a criminal law “must give warning of the conduct it makes a crime.” Traditionally, this requirement was satisfied if (1) the prohibited act was inherently wrongful — such as murder, arson, theft, robbery, or rape — or (2) an individual did something that he or she knew was illegal, even if it was not inherently wrongful.

In recent years, though, federal, state, and local laws that do not meet either requirement but carry criminal penalties have proliferated. Exacerbating the problem, as noted by Ohio State law professor Joshua Dressler in his comprehensive treatise Understanding Criminal Law, “many modern statutes are exceedingly intricate” and “even a person with a clear moral compass is frequently unable to determine accurately whether conduct is prohibited.” As a result, ordinary Americans can be victimized by laws supposedly designed to protect them.

Some overcriminalization incidents can sound amusing until we remember that they involve real people whose lives can be ruined. Last year police charged 46-year-old Ocean Beach, Calif., resident Juvencio Adame with “defacement, damage and destruction” of public property in excess of $400 — charges that could have resulted in significant prison time. His crime? Trimming shrubbery next to his home. Then there’s 17-year-old Cody Chitwood of Cobb County, Ga. Police charged him with a felony for bringing weapons into a school zone. The “weapons” were fishing knives, and they were in a tackle box in Cody’s truck. Georgia law states that any knife “having a blade of two or more inches” is a weapon, and that anyone who carries a weapon onto school property is by that very act guilty of a crime.

“Ignorance of the law is no excuse”? Spare us.

What should we do about this grave threat to our liberties? We can start by addressing the inadequate mens rea (guilty mind) requirements in our criminal law. Legislators must work to identify and repeal or amend laws with insufficient mens rea requirements, and ensure that no such laws are passed in the future.

Additionally, lawmakers should codify interpretive rules that require courts to read meaningful mens rea requirements into any criminal offenses that lack them (unless Congress makes it clear that it intended to enact a strict-liability offense with no mens rea requirement) and should direct courts to apply any existing mens rea term in a criminal offense to each material element of that offense. Legislators should also codify the “rule of lenity” — a judicial rule of interpretation that requires courts to construe ambiguous criminal laws in favor of the accused.

Finally, legislators need to provide an escape hatch for those who were “rationally ignorant” of the law: a mistake-of-law defense in which a defendant would have the burden of producing evidence that he did not know that his conduct was illegal, nor would a reasonable person in his position have believed that the charged conduct was illegal.

Once upon a time, it made sense to insist that ignorance was no excuse for violating the law. Today, that maxim often sounds like a cruel joke. Let’s work to ensure that people are criminally punished only for wrongdoing, not for ignorance of laws that they had no reason to think existed in the first place.

Evan Bernick is a visiting fellow in the Heritage Foundation’s Edwin Meese III Center for Legal and Judicial Studies. This piece originally appeared in National Review Online.