David B. Oppenheimer, Religiosity and Same-Sex Marriage in the United States and Europe, 32 Berkeley J. Int'l L. 195 (2014)
Part I of this paper traces the change in law and attitudes in the United States relating to marriage equality. Part II does the same for Europe. Part III examines the role of the courts in marriage equality. Part IV asks whether we can explain the differences among US and European states by looking at attitudes about secularism and religiosity.
In brief, we recognize that while correlation is not causation, the correlations are dramatic here. In the United States, most of the states that are relatively non-religious or secular now permit same-sex marriage, while most that are highly religious prohibit it. Of the twelve most religious states, all have constitutional bans on same-sex marriage. Of the twelve least religious states, eleven have some recognition of same-sex relationships: eight have same-sex marriage, two have domestic partnerships, and one has civil unions. The same trend is largely true in Europe. We thus conclude that there is a close correlation between religiosity and support for same-sex marriage and that further research is appropriate to examine whether it is causative.