Clergy are officials of the Church. They perform sacred rites such as baptism, communion, worship services, etc. They are paid by non-profit, religious organizations. They stay on the Church side of the separation of the Church and State.
Clergy are not officials of the State. Yet they act as agents of the State when they sign civil marriage licenses. So, in this one case, they stray into the State side of the separation of Church and State. In this one case, they are able to authorize a legally binding contract that gives couples over 1,000 legal rights and benefits. Some of these legal rights and benefits include the ability to file joint income tax returns, receive military benefits for spouses, maintain next-of-kin status for hospital visits and medical decisions, etc.
Marriage licenses required by the State should be separate from the religious ceremonies performed by the Church. We wouldn't want state officials acting as clergy, so clergy shouldn't act as state agents. It's best to let the State be the State - and the Church be the Church. Let their functions be different so that civil marriage is separate from religious marriage. The State should have no part in defining or facilitating religious marriage and the Church should have no part in defining or facilitating civil marriage.
Civil marriage is fundamentally different than religious marriage. Civil marriage includes a legal document that is (or should be) available for all people. It should only be authorized by civil agents in a courthouse. Clergy should not act as a civil official by signing legal documents in a place of worship. On the other hand, religious marriage is a sacred rite for people committed to a particular religion. It should only be performed by religious officials. Clergy should bless marital covenants for religious people in ways that are meaningful to their religious traditions. This separation of civil and religious marriage would help us avoid much confusion in the current debates about marriage.
The Iowa Supreme Court used wise language in their affirmation of "marriage equality" for all couples: "Civil marriage must be judged under our constitutional standards of equal protection and not under religious doctrines or the religious views of individuals." This ruling and these words help to clarify much of the misunderstanding happening in our nation right now. Iowa has made it clear that civil marriage is different than religious marriage.
And, yes, we are proud to be from Iowa!