BUT, even as the book mentions, a state can refuse to honor same-sex marriage contracts, and even as the book states this "poses interesting constitutional questions".
As tacky as this is I'm going to refer to the Merriam-Webster definition of marriage which states "the state of being united to a person of the opposite sex as husband or wife in a consensual and contractual relationship recognized by law"… now my previous use of bold text in the definition of full faith and credit probably makes a bit more sense! Why can't a same-sex couple that gets married in same-sex marriage legal Massachusetts not be recognized as a married couple in their home-state of Texas? This is not only discriminatory… but it is unconstitutional.
Because the 10th amendment hands over all rights not given to the national government to the state governments, marriage is handed over like a worthless penny laying on the street for the states to choose as they please.
Of course either way a gay couple that has been together can still have more love than a legally bound Las Vegas pair (as represented by the political cartoon above)…but this can become an issue in situations like if one partner is sick and the other wants to visit them in the hospital, or in situations where a couple wants to adopt a child.
In a related current case, the illegality of gay marriage and it's lack of recognition between states has caused controversy in "Adar vs Smith"… this is not just some textbook case, this is a current case that is relevant to our time. After legally adopting their Louisiana-born child in the state of New York, Oren Adar and his partner Mickey Smith were told by the Louisiana state registrar that she would not issue a new birth certificate for their child, because Louisiana does not recognize adoption by unmarried parents. Eventually this was seen to have violated the Equal Protection Clause of the 14th amendment but the attorney against the couple stated that "she did not have to honor an adoption from another state that Louisiana would not have granted under Louisiana law if the couple had lived and adopted there"… A U.S. district judge ruled that this conduct did not comply with the full faith and credit obligation and the parents were issued a birth certificate with both names as parents. In this case full faith and credit was pulled through… but why hasn't it been taken into account for recognizing the sacred union between two lovers?
Until somebody else sues for this right, Full Faith and Credit will not be able to fufill it's current and relevant purpose in this century, causing myself to believe that full faith and credit its just full of…………….
(in the most polite way possible)