The Church of England is in a bit of a weird position here. It's not so much that Parliament has unilaterally decided that the C of E shall not perform same-sex

The Church of England is in a bit of a weird position here. It's not so much that Parliament has unilaterally decided that the C of E shall not perform same-sex marriages, but that, as the established Church with the monarch at its legal head, it is as much a creature of advised royal decree and legislation as it is of the 39 Articles or the General Synod (represented by Canterbury). That results in areas of church law originating outside of Parliament winding up in legislation.