To talk about lying as a crime, we have to step back and ask "what's a crime?"

There are at least four possible answers: (1) it violates a law, (2) it violates the ten commandments; (3) it's morally repugnant, and (4) it hurts other people.

Violating any one of these will cause someone to call an act a crime, and others will disagree, rightly or wrongly.

Lying violates all of these, if the lie is evil enough.

The obvious problem is enforcibility.

Sadly, many if not most people think "if you can't enforce it, it's not a crime."

That's false. Unenforceable just means it's unenforceable.

A crime is a crime, whether it's enforceable or not.

I'm not advocating enforcement per se. I can't think of an enforcement that would work.

On the other hand, if it's a crime, it deserves to be called a crime.

A crime is not OK because it's unenforceable.

It's worth making that distinction.