The above quote comes directly off the DoS website...are you saying they are wrong? In any case the immigrant visa will be issued already and in the person's passport - and once there is a valid visa it is not up to the person at the POE to decide if it should have been issued or not, only to process the person in accordance with their valid visa.
You are right.
http://www.uscis.gov/portal/site/us...nnel=2543215c310af310VgnVCM100000082ca60aRCRD
Q3: My spouse and I were married in a U.S. state or a foreign country that recognizes same-sex marriage, but we live in a state that does not. Can I file an immigrant visa petition for my spouse? NEW
A3: Yes. As a general matter, the law of the place where the marriage was celebrated determines whether the marriage is legally valid for immigration purposes. Just as USCIS applies all relevant laws to determine the validity of an opposite-sex marriage, we will apply all relevant laws to determine the validity of a same-sex marriage..
http://travel.state.gov/visa/frvi/frvi_6036.html
Q: Do we have to live or intend to live in a state in which same sex marriage is legal in order to qualify for an immigrant or nonimmigrant visa?
A: No. If your marriage is valid in the jurisdiction (U.S. state or foreign country) where it took place, it is valid for immigration purposes.
So, today that is allowed.
However,
http://www.state.gov/documents/organization/86920.pdf contains a clause:
The underlying principle in determining the validity of the marriage is that the
law of the place of marriage celebration controls (except as noted in paragraph
d of this section). If the law is complied with and the marriage is recognized,
then the marriage is deemed to be valid for immigration purposes. Any prior
marriage, of either party, must be legally terminated.
This is what you quoted. Further
Marriages, considered to be void under State law as contrary to public policy,
such as polygamous or incestuous marriages, or which Federal law such as the
Defense of Marriage Act determines does not meet the Federal definition of a
marriage, cannot be recognized for immigration purposes even if the marriage
is legal in the place of marriage celebration
I am not sure how federal law treats child marriages. But the situation should be similar to same sex marriages.
If they are both banned by a state, like in Texas
http://blog.veritaslegalgroup.com/2011/12/11/voidable-marriages-in-texas-houston-divorce-lawyers/
In addition to the above, Texas does not recognize child-marriages under the age of 16, even with parental consent.
So, if the state treats same sex marriages as contrary to public policy, the marriage cannot be recognized for immigration purposes, if the intended destination is that state. I am not sure if Texas voids child marriages as contrary to public policy or just voids them on other reasons. If it is as contrary to public policy, the marriage is not recognized for immigration purposes, whatever the DOS website says by mistake.
State has jurisdiction to void same sex marriages as contrary to public policy. Even if none of the states does it today (what means they do it on other reasons; we know some states do it), they could do it tomorrow on that reason. In that case the visa that was already given, would be voided automatically.
So, until all states determine their points of view, just ignore those states in your immigration process. Do not to intend to live in those states, and have a proof where you intend to live. That proof might be needed at the consulate and at POE. Do not try to enter US through a state like that if you enter on an immigrant visa (when you enter US later, with GC, it does not matter).