What if other religions conduct a gay marriage ?

Christian conservatives say that marriage is a religious institution and must be seperate from government .As such they don't support efforts to legalise gay marriage as Christianity,Judaism,Islam dosent support it . However what if a Hindu or Buddhist or Jain wants to officiate a gay marriage isn't he using his freedom of religion , if you don't recognise it you are not recognising a religious marriage . What about several churches that allow same sex marriage , sure they may not be Christian but they are religious institutions . If u say it is only a Christian institution would u recognise a non christian marriage in a Christian majority country ?