Book excerpt: During the past three decades, nations all over the world have been debating whether to allow same-sex couples to marry, or at least grant these couples various rights associated with marriage. In Equality for Same-Sex Couples, Yuval Merin presents the first comparative study of the legal regulation of same-sex partnerships worldwide, as well as a unique survey of the status of same-sex couples in Europe. Merin begins by providing a historical overview of the transformation of marriage from antiquity to the present. He then identifies and critically compares four principal models for the legal regulation and recognition of same-sex partnerships: civil marriage, registered partnership, domestic partnership, and cohabitation. Merin concludes that all of the models except civil marriage discriminate against gays and lesbians just as the "separate but equal" doctrine discriminated against African Americans; thus, so-called alternatives to marriage, even if they provide the same rights and benefits as marriage, are inherently unequal and therefore unconstitutional.