The Archdiocese of Saint Paul and Minneapolis and the Minnesota Catholic Conference recently clarified that a group posing as a Catholic group isn't actually Catholic:
The Archdiocese of Saint Paul and Minneapolis and the Minnesota Catholic Conference issued a joint statement today explaining that a newly formed group calling itself “Catholics for Marriage Equality MN” has no recognition from nor affiliation with the Roman Catholic Church.
One of Catholics for Marriage Equality MN’s expressed aims is to defeat the Minnesota Marriage Protection Amendment that will appear on the November 2012 ballot, and which defines marriage as the union of one man and one woman. The group misleadingly tries to convince Catholics that they can, in good conscience, support a state redefinition of marriage without undermining marriage itself. The Catholic Church, in keeping with Catholic teaching, reason and natural law, and in concert with many other faiths, strongly supports maintaining the current, traditional definition of marriage by voting “yes” for the Amendment during the November 2012 election.
The press release also charges that Catholics For Equality is guilty of misrepresenting and diminishing Catholic teaching:
Both MCC and the Archdiocese stress the importance of respecting the God-given dignity of all persons, which means the recognition of authentic human rights and responsibilities, while pointing out that official Catholic teaching goes well beyond what Catholics for Marriage Equality MN’s website states.
Outside groups are free to say what they want, but they aren't free to decide what Catholic teaching is.