If a prenuptial agreement is on the to-do list before the wedding, think very carefully and read closely before signing. Once signed, pre-nups are very hard to break legally. Those cautions come from experts who specialize in unwinding those binding contracts when things don't work out as planned. Voiding a properly drafted and signed prenuptial agreement in search of a better deal is difficult, they say, but not impossible.
The easiest way to get a pre-nup declared null and void is to find a paperwork error. Of course, if the document was drafted by a lawyer who knows how to do it properly, the chances of finding a valid error are pretty small. Another "out" is discovering that a spouse significantly misrepresented his or her assets. In different states, courts will interpret "misrepresented" differently. For example, if a spouse with hundreds of millions in assets fails to mention another five million squirreled away in a rainy-day fund, a judge could consider that a minor misrepresentation. A spouse who claims to have few assets but is actually sitting on millions might provoke the judge enough to void the agreement. Proportionality is the key.
Coercion is another avenue to invalidating a pre-nup. However, the evidence had better be very strong. "Literally, you'd have to have a gun next to your head," says Philadelphia divorce attorney David Steerman, and proving coercion is difficult. The last easy out is unenforceable provisions that would break the law or be far out of the mainstream. "It would have to shock the conscience and be something that nobody in their right mind would agree to," is the example offered by another veteran of the prenuptial agreement wars.
Remember also that state law and the judicial traditions of the local courts will weigh heavily on whether dissolution will be allowed. Don't count on oddball clauses -- restrictions on a partner's weight gain or food preferences, how often relatives can visit or monetary penalties for infidelity are generally not considered deal-breakers. With enough time and legal firepower a pre-nup may be broken, but the experts say that is the exception rather than the rule.
Source: Reuters, "Breaking up is hard to do, breaking prenup is harder," Geoff Williams, Oct. 5, 2012