As of January same sex couples will be able to marry there after an intervention by politicians in Westminster while the Northern Ireland Assembly is in stalemate.
According to CI, the changes go much further than current laws in Great Britain with fears there won't be protection for church ministers who object.
CI is calling for the law to be exactly the same as the rest of the country, ensuring freedom of religion, freedom of expression and freedom of association.
CI spokesman Simon Calvert said: "Same-sex marriage is about to be legalised from 13 January and proper protections for those who disagree will not be in force. That's the implication of what the Northern Ireland Office (NIO) says.
"Parliament took the best part of a year to debate introducing same-sex marriage in England and Wales. For Northern Ireland, MPs took only a couple of hours. In the rest of the UK there are many protections for those who disagree with same-sex marriage. Not so in Northern Ireland, with the Secretary of State and the NIO not seeming to be bothered.
"Churches must not be sued if they refuse to do a same-sex marriage and public order law must be amended to stop church ministers being prosecuted for sermons that disagree with same-sex marriage. The new law has to make this clear."
Currently any church leader in the rest of the UK unwilling to conduct a same sex marriage is protected, for example, the Church of England.
The United Reformed Church and the Episcopal Church in Scotland have already conducted gay weddings.
The Methodist Church is expected to follow suit next year.
Premier has contacted the Northern Ireland Office and is waiting for a response.
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