The Supreme Court's decision earlier today to hear the four gay marriage cases out of Kentucky, Michigan, Ohio, and Tennessee sets the stage for the the constitutionality of same-sex marriage bans to be decided once and for all.

With the high court's previous DOMA ruling in place and its refusal to stay lower court rulings bringing marriage equality to a number of states, it can be tempting to think nationwide marriage equality will be a sure bet this year.

For precautions sake though, Lambda Legal's Jon Davidson has spelled out what will happen should SCOTUS go the other way:

If the Supreme Court were to rule in the cases in which it today granted review that the U.S. Constitution does not protect same-sex couple's right to marry and does not require states to respect marriages same-sex couples lawfully have entered in other jurisdictions, a number of issues would arise.

With respect to same-sex couples who already have married as a result of court rulings, Lambda Legal strongly believes — as a federal district court in Michigan ruled just yesterday with respect to marriages entered in that state before the 6th Circuit's adverse ruling — that those marriages will remain valid and will need to continue to be respected by the states in which those marriages were entered. Nonetheless, the validity of those couples' marriages may be challenged and those couples may want to take additional steps (such as executing wills, durable health care powers of attorney, and securing second parent adoptions) to provide them and their families extra peace of mind and security.

With respect to whether same-sex couples would be able to marry and would have their marriages respected in other states, that would vary from state to state. States in which marriage equality was achieved by a ruling under the state's constitution, by legislative reform, or at the ballot box, would be unaffected. Unmarried same-sex couples in Kentucky, Michigan, Ohio, and Tennessee (the states whose marriage laws the Supreme Court today agreed to review) would be forced to seek reform through the political process. States in which a final judgment has been obtained in federal court would be required to continue to allow same-sex couples to marry and to respect out-of-state marriages entered by same-sex couples unless and until someone with standing makes a motion to reopen the judgment and that motion is granted (unless stays are properly obtained before then). In some states, there may be no one with standing interested in seeking to set aside the existing judgment. Same-sex couples in states in which a judgment is on appeal or can still be appealed whose judgments have not been stayed should be able to continue to marry and to have their out-of-state marriages honored by the state until the existing judgment is stayed or reversed.

There's no question that it would be a mess. This is one additional reason why the Supreme Court should reverse the 6th Circuit's aberrant decision and hold that same-sex couples, like all other couples, share the fundamental right to marry and that it violates federal guarantees of equality and liberty to refuse to allow them to marry or to deny recognition to the marriages they lawfully have entered in other states.

If you haven't already, be sure to check out our legal editor Ari Ezra Waldman's analysis of today's events HERE.