Not an issue, according to Levin.
A SCOTUS decision in the thirties assured that one state's decision in a discretionary matter -- such as marriage -- could not force another state to act outside its own laws.
Indeed, DOMA re-affirmed this decision.
Texas, for example, is under no obligation to accept or recognize a same sex "marriage" from Massachusetts.
Is Nebraska, with a marriageable age of 17 required to accept a marriage of a 21 year old man and a 13 year old "woman" (with parental consent) from New Hampshire (yes, that is apparently legal in NH)?
Or does Nebraska put the 21 year old away for statutory rape?
Article IV Section 1 says the former.
If it came up before SCOTUS, I would imagine that SCOTUS would use the same principle for homosexuals.