I remember some discussions with the erstwhile love of my life (TELOML), who was a law student at the time. Actually, I understand that she is again, but that's another matter.

No contract can depend on an immoral act. This actually came up as part of an explanation of why premarital contracts aren't considered valid contracts in Britain. So logically, indeed no court would try to enforce such a deal. I don't know of any specific cases, though.