JTN: I don't see a role for the government in marriage at all.
The United States Supreme Court has already decided against you both:
"Laws are made for the government of actions, and while they cannot interfere with mere religious belief and opinions, they may with practices..."[Reynolds v. United States, 98 U.S. 145, 8 Otto 145, 24 L. Ed. 244 (1878).]
See also: Late Corporation of the Church of Jesus Christ of Latter-Day Saints v. United States, 136 U.S. 1, 10 S.Ct. 792, 34 L. Ed. 478 (1890). Revised as 140 U.S. 665, 11 S.Ct. 884, 35 L. Ed. 592 (1891).
Marriage is a religious "rite," not a civil "right;" a secular standard of human reproductive biology united with the Judaic Adam and Eve model of monogamy in creationist belief. Two homosexuals cannot be "monogamous" because the word denotes a biological procreation they are not capable of together. Human reproductive biology is an obvious secular standard.
It was landmark U.S. Supreme Court precedent Reynolds v. United States in 1878 that made "separation of church and state" a dubiously legitimate point of case law, but more importantly; it confirmed the Constitutionality in statutory regulation of marriage practices.
Congress, state legislatures and public referenda have statutorily determined polygamous, pederast, homosexual, and incestuous marriages are unlawful. No Constitutional Amendment restricting marriage is required to regulate "practice" according to the Reynolds decision.
All adults have privilege to marry one consenting adult of opposite gender; therefore, Fourteenth Amendment "equal protection" argument about "privileges and immunities" for homosexual marriage is invalid. Driving, marriage, legal and medical practices are not enumerated rights; they are privileged practices that require statutory license.
Nothing that requires a license is a right.
Homosexual monogamy advocates are a cult of perversion seeking ceremonious sanctification of preternatural prurient preferences for voluntary deviancy with anatomical function. It is not a logical basis to claim societal privileges; it is a religiously psychotic appeal for esoteric absolution.
Kind of like sucking babies brains out of their skulls...but hey the SCOTUS says it's ok, so that makes it ok. So if SCOTUS says that Marriage is a Federal Issue then by God that just settles it.
L