This paper analyzes the complex issue of defining marriage through the lens of legal philosophy. Equal protection analysis and due process analysis are central tenets of marriage jurisprudence. The reluctance of the federal government or Supreme Court to weigh in decisively on the constitutionality of bans on same-sex marriage yields, on the state level, a legal landscape of considerable variety. Thus, this paper creates a scheme of classification to organize and understand the various political and judicial methods that states employ to define legal marriage. While some states view homosexual relationships with an eye of moral disapproval, others have contended that homosexual relationships are worthy of respect, dignity, and, ultimately, legal recognition. To evaluate the strengths and weaknesses of arguments for and against same-sex marriage I draw on a variety of resources including books on constitutional interpretation, law review papers, campaign materials and other items. After reconstructing the dominant legal strategies used in same-sex marriage litigation, and analyzing the most prominent arguments in the political arena, I argue that the courts should render unconstitutional state constitutional amendments or statutory schemes that define marriage as exclusively heterosexualon the basis that bans on same-sex marriage violate equal protection and due process guaranties found in the federal constitution and almost all state constitutions.