At the Heart of it is a Contract.
More possible changes in law over prenups. An unusal case is taking place in Texas where a wife of a wealthy hedge fund manager is making the arguement that she should be entitled to damages for ex's violation of a prenup. However did she have "unclean hands" because she too violated the prenup? Interesting case to watch http://nypost.com/2013/11/29/hedge-fund-manager-in-epic-divorce-battle-over-prenup-violations/