750.505 Punishment for indictable common law offenses.
Any person who shall commit any indictable offense at the common law, for the punishment of which no provision is expressly made by any statute of this state, shall be guilty of a felony, punishable by imprisonment in the state prison not more than 5 years or by a fine of not more than $10,000.00, or both in the discretion of the court.
How many people who aren't attorneys know what common law even is? It's judge made law. Law in Michigan is based on the English Common Law system. Common law is modified by judges when there is no statutes. Criminal law statutes are often based on common law and codified. That's good so people can supposedly know when they are breaking the law. Common law is often used in torts, contracts, and property cases. That's nothing unusual and the common law is often based on old customs to reduce surprises. In criminal cases, this is bad because theoretically, we need to be sure what the law is so we don't end up in prison.
This law was actually attempted to be enforced against the late Dr Jack Kevorkian. I'm not a fan of Dr Death at all, but this was a ridiculous attempt by the prosecutor's office in Oakland County. This ended in acquittal, likely a case of jury nullification, which is not always a bad thing.
Dr. Jack Kevorkian today was found not guilty of violating Michigan common law against assisted suicide, closing two cases that his lawyers said were by far the most significant of the five acquittals he has won at three trials.
The 1994 Supreme Court, much more liberal than the current court due to the Blanchard and Milliken judges, said that "assisted suicide" wasn't a right (which is understood) but also a "common law crime based on custom" opening this up. Common law crimes federally were abolished in 1812 although things vary among the states.
Crimes need statutes, penalties, and jurisdiction. The old saying is that ignorance of the law is no excuse, but it shouldn't take an attorney to understand if one is breaking the law, especially for a felony. Just because something isn't usually enforced does not mean it isn't on the books and could be enforced at a later date if prosecutors are out to get someone.