In all of the many branches of the Christian religion, gay marriage is illegitimate. If any same sex couple was to marry in a Church, the marriage is void because all sects do not dignify this action as a real sacrament.
Gays should be allowed civil marriages, but no liberties to a marriage certificate. A marriage certificate entails that the sacrament of marriage is respected. Same sex marriage does not respect this sacrament.
The government should not enforce that Churches are required to marry same sex couples.