[Glenn]

but it is not illegal to breach a contract.

What? A contract is a legal agreement. To breach it is "illegal" by definition. Just what the hell do you teach?

[Roscoe]

Probably not contract law.

[mountaineer]

Breaching an employment contract is not considered a violation of law. Yes, I am a lawyer.

[Teacher317]

I taught 8th grade math... however, my Contracts Law professor has repeatedly stated that breaching contracts is not a criminal act. It happens all the time. As long as you pay non-breaching party for the loss they incurred (or the expected profit that you suddenly denied them), there is no crime.

Two private parties signing a contract does not create a new law whose violation qualifies as an "illegal" act.