1 There is no basis for the concerns expressed by some MPs during the Second Reading Debate in the House of Commons last week  that there may be good legal cause why this man and this man (or this woman and this woman) should not be joined together in matrimony.
worth reading in full at http://www.publications.parliament.uk/pa/cm201213/cmpublic/marriage/memo/m01.htm
5 Concern has been expressed that the European Court may challenge the special position of the Church of England and the Church in Wales, which cannot opt-in to same sex marriage, like other religious bodies. But the special treatment of those Churches is plainly justified. It arises from the common law duty of the clergy to marry a parishioner in their parish church. If the Church of England wishes to solemnise marriages of same sex couples, it may put a Measure before Parliament to change the law relating to it. The Church in Wales (being disestablished) cannot take such a step and so the Bill contains a power for the Lord Chancellor, by order, to amend the law if the Governing Body of the Church in Wales so requests.
6 The suggestion that parents, teachers and foster carers may be subjected to detriments because of their views on same sex marriage are unfounded. The law contains protection for religious beliefs and practices, and for freedom of expression, and in any event the Bill does not adversely affect the content of the law in such contexts.
7 It is true that the Bill will not protect marriage registrars who have religious objections to conducting same sex civil marriages. In 2009, the Court of Appeal dismissed the claim of a registrar, Ms Lillian Ladele, that she was entitled, on religious grounds, to refuse to be involved in conducting civil partnership ceremonies.  Last month, the European Court gave judgment dismissing Ms Ladele's claim under the European Convention.  If you are employed as a marriage registrar performing public functions, you cannot refuse to perform a part of those functions because you disagree with the law of the land as to who may get married. That was the basis of the judgments of the Court of Appeal and the European Court of Human Rights.
8 For the reasons set out above, the arguments of those who oppose the Bill are not assisted by legal concerns.