Just you wait. I guarantee you it won't be long until gay marriage gets challenged in the Supreme Court under the Full Faith & Credit Clause of the Constitution. I'll bet you a buck gay marriage bans get overturned.
I had the unusual opportunity to take a constitutional law class from a strongly conservative professor who personally opposes gay marriage. He said that even though he hates the idea of gay marriage he believes that under a strict interpretation of the Constitution all gay marriage bans are unconstitutional.
The Full Faith & Credit Clause of Article 4, Section 1 of the Constitution says "full faith and credit shall be given in each state to the public acts, records, and judicial proceedings of every other state." Legal contracts are "public acts" and that includes marriage contracts. The Full Faith & Credit Clause requires all states to recognize any legal contract formed in another state. Massachusetts issues marriage contracts. All it will take will be for a gay couple to get married in Mass. and then move to another state and try to get their marriage legally recognized. If they are denied legal recognition they will have grounds to go to court.
My conservative con law professor said that even though he hates gay marriage, if he were a judge and such a case came before him he would be forced to strike down gay marriage bans because they violate even the most limited interpretation of the Full Faith & Credit Clause. He also said that the federal Defense of Marriage Act is unconstitutional for the same reason.
This is why a gay marriage ban to the federal constitution is the only way the battle will ever be truly won. Mark my words gay marriage bans WILL be challenged someday before the Supreme Court and the smart money says that even the conservative will be forced to acknowledge the literal truth of the Full Faith & Credit Clause.
Since government has perverted the original intent of the law and now forces the people to get governments PERMISSION (a.k.a. license) in order to be *legally* married, I fear your professor is right.
I think you are absolutely right: the statewide bans will be legally meaningless in this court-dominated nation.