Marriages were never intended to be religious rituals or practices. In ancient Rome, marriage was a civil matter and fell under the jurisdiction of imperial law. 
Therefore, marriage was a legislative matter long before it was a religious matter.
There are also now openly gay Judeo-Christian religious figures. Reform and Conservative Judaism endorse same-sex marriage, as does the United Church of Christ. Any biblical interpretation that asserts that homosexuality is a sin is an outdated interpretation of the Bible. As such, governments are free to allow gay marriage or civil partnerships.