Chelsea Clinton's Cheat-Proof Prenup (we love it)

As the daughter of a man who creamed Tiger Woods in the sex scandal department, Chelsea Clinton will not be cheated on cheaply. Flashing new engagement bling these days, she's made her fiance, Marc Mezvinsky, sign a prenup that says if he has sex with another woman, it will cost him $10 million.

"Chelsea's world was shattered when she learned that her father had been unfaithful to her mom," a source told The National Enquirer, which broke the news, "...not once, but many times, [and it] made her very gun-shy about trusting the guys she dated."

Apparently, she's not the only one who is protecting her fidelity investment: Rumor has it that Denise Richards and Charlie Sheen signed a prenup with a $4 million cheating price tag, and that Catherine Zeta-Jones put a similar clause in hers with Michael Douglas. Even Sandra Bullock's prenup states that if Jesse James fools around on her, he'll get zilch, according to Radar online. (For the love of women, Sandra, please don't let him get away with a cent.)

Infidelity is not the only personal issue cropping up pre-marital agreements. In a HuffPo blog, attorney Nina Kotick, ticks off all kinds of weird clauses. A couple might specify how often they must have sex-even mandatory positions, she writes. Or a clause might prohibit "one spouse (guess which one) from gaining too much weight and impose a fine for each excess pound."

Lawyers point out that most of these so-called lifestyle clauses are hard to enforce, because what court is going to get involved in a dispute over weight, or whether someone refused to do it doggie style. But cheating may have more traction. "I don't see why it wouldn't be enforceable and valid if brought up before a court, as long as you can prove it, says Maggie Kaminer, a New York City matrimonial lawyer, who by the way, will be my lawyer, next time I get divorced. (Her firm consists of three mom-attorneys who went out on their own so they'd have more flexibility to raise their young kids. Way cool.)

If you're thinking about a prenup with, or without, a cheating clause, here are a few pointers:

Are the online forms cool? No. Not if you want cover your ass (and your assets.) Each state has its own laws, and each couple has different financial complications, and without legal representation on the front end, it's too easy for him to wiggle out of things on the back end. The reason these documents often don't hold up in court is because one spouse says, "I never read it," or "I didn't really understand what I was signing," or "I was pressured to sign it."

That's why you both need an attorney. You can initiate a draft with your own lawyer, but once it's done, your husband-to-be must have someone who represents his interests look it over.

What if he says, "I don't need a lawyer"? "Then he's going to have to sign a waiver letter," says Kaminer. "And that letter states that a) he's got a right to an attorney, b) he's been advised to get an attorney, and c) he's waiving that right. Or else, no go. Because later on, if there's a question of validity, and he says, 'I didn't have a lawyer, I didn't know what I was doing, I didn't understand,' we say, 'Sorry buddy, you signed this waiver."

And if you're already married sans prenup (and kicking yourself)? Here's a little idea to keep in your back pocket. When NYPD Blue actress, Garcelle Beauvais-Nilon, discovered her Hollywood agent hubby had a mistress, she sent an email around his high-powered office with the subject line: "Tiger Woods/Jesse James/Mike Nilon."

"What do they have in common...," the text of the email went on. "I found out today that MY husband of 8 yrs has been having an affair for 5 yrs with some slut in Chicago. I am devastated!!!! And I have been duped!! Our boys don't deserve this!"

You know, I might have toned down the "devastated" and gone for something like: "If he can dupe his family, think how he might be cheating you. Do you want a skunk like this ruining your agency's reputation? " But hey, it was a ballsy move, and one I'd consider copying.

What do you think about prenups? Would you put a cheating clause in yours?

For more advice on prenups, read:

Why you should have one

Nuts & Bolts

5 Insights from a high-stakes lawyer

[Photo Credit: Getty Images Entertainment]