Going back a few hundred posts back on this thread, you will find the following:
Despite the basic rule that a marriage valid where contracted is valid everywhere, the courts and validation statutes have universally recognized a number of exceptions, which may be condensed and simply stated as follows: A marriage valid where contracted will nevertheless not be recognized as valid in the forum state if such recognition would be contrary to a strong public policy of the forum state. Restatement (Second) of Conflict of Laws 283(2) comment f (1971) (marriage valid where contracted will be recognized as valid everywhere unless it violates the strong public policy of another state which has the most significant relationship to the spouses of the marriage); e.g., Fattibene v. Fattibene, 183 Conn. 433, 441 A.2d 3 (1981) (Connecticut need not recognize marriage that violates strong public policy of state); In re Estate of Loughmiller, 229 Kan. 584, 629 P.2d 156 (1981) (listing exceptions to validation statute, including marriage that is polygamous, incestuous, or prohibited by the state for public policy reason); K. v. K., 90 Misc. 2d 183, 393 N.Y.S.2d 534 (Fam. Ct. 1977) (court called upon to decide whether law of Poland, which requires civil ceremony in addition to religious ceremony, was repugnant to law of New York); Kelderhaus v. Kelderhaus, 21 Va. App. 721, 467 S.E.2d 303 (1996) (general statement that marriage's validity is to be determined by law of state where marriage took place, unless result would be repugnant to Virginia public policy).There are three commonly recognized categories of marriages contracted in another state that will not be recognized in the forum state. First, marriages that are contracted by domiciliaries of the forum state in another state for the express purpose of evading the law of the forum state are deemed invalid. E.g., Loughran v. Loughran, 292 U.S. 216 (1934) (marriage entered into in Florida, in violation of D.C. prohibition against remarriage within certain amount of time after prior divorce, invalid in D.C.); Barbosa-Johnson v. Johnson, 174 Ariz. 567, 851 P.2d 866 (Ct. App. 1993) (appellate court holding that evidence did not sustain finding that parties had married in Puerto Rico for the purpose of evading the law of Arizona). See generally Uniform Marriage Evasion Act, 9 U.L.A. 480 (1942) (N.B.: The Uniform Marriage Evasion Act is superseded by the Uniform Marriage and Divorce Act, and was officially withdrawn from consideration by the drafters in 1943).
Second, states have refused to recognize marriages that are solemnized in sister states when the parties are of a level of sanguinity that is forbidden in the forum state. E.g., McMorrow v. Schweiker, 561 F. Supp. 584 (D.N.J. 1982) (rule recognizing foreign marriages does not apply to incestuous marriages); Catalano v. Catalano, 148 Conn. 288, 170 A.2d 726 (1961); In re May's Estate, 305 N.Y. 486, 114 N.E.2d 14 (1953).
Third, states have refused to recognize marriages that are solemnized in sister states when the parties are not deemed of sufficient age to marry, as determined in the forum state. E.g., Wilkins v. Zelchowski, 26 N.J. 370, 140 A.2d 65 (1958).
Given this strong tradition of a state's right to refuse to recognize a marriage validly contracted in another state if that marriage would offend the fundamental public policy of the state, there appears to be no reason for enactment of the Defense of Marriage Act. The states already have the ability to refuse to recognize a same-sex marriage should they so choose. A state's public policy regarding same-sex marriages may be adduced from the presence or absence of both statutory prohibitions and decisional authority regarding same-sex marriages. E.g., Uniform Marriage and Divorce Act 201, 9A U.L.A. 170 (1987) (defining marriage as a personal relationship between a man and a woman).
This is the present legal status quo, Luis. As long as the 14th Amendment is also the law of the land, in any conflict between a state vis-a-vis same-sex marriage contracted in another state, and the way SCOTUS seems to be interpreting the "privileges and immunities" clause these days (i.e., as against state interest), which side do you think would prevail in that fight? Especially since, as Justice Scalia recently pointed out, the present ruling shooting down Texas law seems to put all forms of state prohibitions of marriage (polygamy, incest, underage, consanguinity, etc.) on shaky ground.