That has implications for all of us.

By way of background, financial institutions are required to report all transactions of $10,000 or more to the federal government. This is meant to make it harder to commit racketeering, tax fraud, drug crimes, and other serious offenses. Hastert began paying off the person he allegedly wronged years before by withdrawing large amounts of cash. But once he realized that this was generating activity reports, he allegedly started making more withdrawals, each one less than $10,000, to avoid drawing attention to the fact that he was paying someone for his silence.

Again, the payments weren’t illegal. But as it turns out, structuring financial transactions “to evade currency transaction reporting requirements” is a violation of federal law.

To see why that is unjust, it helps to set aside Hastert’s case and consider a more sympathetic figure. Imagine that a documentary filmmaker like Laura Poitras, whose films are critical of government surveillance, is buying a used video camera for $12,000. Vaguely knowing that a report to the federal government is generated for withdrawals of $10,000 or more, she thinks to herself, “What with my films criticizing NSA surveillance, I don’t want to invite any extra scrutiny—out of an abundance of caution, or maybe even paranoia, I’m gonna take out $9,000 today and $3,000 tomorrow. The last thing I need is to give someone a pretext to hassle me.”*

That would be illegal, even though in this hypothetical she has committed no crime and is motivated, like many people, by a simple aversion to being monitored.

I don’t much like the $10,000 reporting requirement: as I see it, behavior that lots of people engage in every day for perfectly legal reasons shouldn’t trigger surveillance. And it is certainly perverse to set a threshold for government scrutiny, only to make it a criminal offense to purposely avoid triggering that threshold.

Think of applying the same logic in another context.

What if the government installed surveillance cameras on various streets in a municipality and then made it a crime to walk along a route that skirted those cameras?

Of course, Hastert may also have committed more serious offenses. The current charges could be motivated by a desire to prosecute him for sex crimes. But that dodges the issue.

“In order to punish him for that crime, the government should charge him with it, then prosecute him with due process and convict him in front of a jury of his peers,” Greenwald argues. “What over-criminalization does is allow the government to turn anyone it wants into a felon, and thus punish them without having to overcome those vital burdens. Regardless of one’s views of Hastert or his alleged misconduct here, it should take little effort to see why nobody should want that.”

If the state can decide that specific, legal behavior will trigger scrutiny by federal law enforcement and that any attempt to avoid that scrutiny is illegal, even if no other crime is proved, everyone’s privacy and freedom from unjust arrest is undermined.

*A previous version of this article had a different hypothetical that might not have triggered the reporting requirement.