So California’s Proposition 8 is gone. A coalition of liberal and conservative justices decided today that they did not have to decide the question they had just decided because the party that they authorized to stand up for Proposition 8 lacked the standing to stand there. At the same time, a very different Supreme Court majority, split along traditional liberal-conservative-Kennedy lines, invalidated the Federal Defense of Marriage Act—not, as some people anticipated, on narrow procedural grounds, but on a fairly sweeping interpretation of the Fifth Amendment’s Due Process clause.

Both rulings support what we used to call “state’s rights” but now (quite incorrectly) call “federalism” because “state’s rights” sounds too Jim Crow-y. States, it appears, are free to define marriage however they want, to marry whoever fits their definition, and to rest secure in the knowledge that the federal government will recognize whatever they choose to do. Vox Provinciae, Vox Dei.

And this is the beginning of the next big marriage battle—one that will have profound consequences for what we mean when we say that we are a nation.

States have been creating the lines for the coming battle for quite some time. By the end of the summer, fourteen jurisdictions (thirteen states and the District of Columbia) will permit same-sex couples to marry with all of the privileges and immunities of opposite-sex couples. Seven states currently have laws against same-sex marriage, and thirty more have constitutional provisions that prohibit recognition of same-sex marriages performed in other states.

What this means in practice is that there will soon be a lot more lawsuits. Thirty states will be required by their own constitutions to deny marriage benefits to residents who have been legally married in other states. All of the couples so denied will have “standing.” Many of them will sue in federal courts. Some of them will win.

They will win, I believe, because they have a very compelling argument under Article IV, Section I of the Constitution, which says that “full faith and credit shall be given in each state to the public acts, records, and judicial proceedings of every other state.” You know, like marriage.

Now, this is no slam dunk. There is a long legal tradition of applying the Full Faith and Credit Clause rigorously to court judgments but much less rigorously to state laws. There are certainly the legal precedents—if anybody wants to get caught invoking them—of runaway slave laws and pre-Loving v Virginia (1967) anti-miscegenation laws. In the past, we have allowed states to have different definitions of the word "marriage” and even of of the word “person"--but this has rarely worked out very well.

And there is only limited refuge here for the states, even if they are willing to cite the devil to win a precedent. The legal definition of marriage bears directly on the types of legal judgments—about things like property rights, child-custody decisions, contracts, inheritances, etc.—that constitute the core purpose of the Full Faith and Credit Clause. The federal court system is going to have no shortage of difficult (and extremely interesting) questions to decide as these cases work their way through the system.

In the meantime, marriage is going to be a mess pretty much everywhere. Just imagine, for example, what will happen if the State of New York decides it will no longer recognize any marriages performed in states that do not recognize its marriages. And that's just for starters. Imagine what will happen if they stop recognizing divorces. Are any of us going to be comfortable knowing that we could be living in sin, or even committing bigamy, any time we cross a state line?

Today’s decisions put us on the road to one of those “house-divided” moments that Abraham Lincoln was always talking about. Thirty states now have a constitutional requirement NOT to recognize the legal actions of other states—this is a condition appropriate for a loose confederacy like, say, the Eurozone or the Delian League, but it is not how actual nations are supposed to work. The purpose of the Full Faith and Credit Clause is to prevent precisely this kind of situation from arising or being allowed to continue. Both Madison and Hamilton believed that, if we cannot be secure in our legal standing from one state to the next, we are not citizens of anything that can legitimately be called a nation. The next marriage battle, therefore, will not be about inheritance rights and property divisions; it will be about whether or not we are a country.