A pre-nup is an agreement in which fiancés jointly make provisions regarding spousal support and the distribution of assets should they divorce in the future. A postnup is a similar instrument that spouses (or registered domestic partners) enter into during a marriage. The enforceability of prenuptial agreements is governed by Family Law Code section 1615. Due to enforceability issues, it is crucial to have your prenuptial agreement drafted by a knowledgeable family law attorney.