Marriage in the United States shall consist only of the union of a man and a woman. Neither this Constitution or the constitution of any State, nor state or federal law, shall be construed to require that marital status or the legal incidents thereof be conferred upon unmarried couples or groups.
What is in a Word?
Marriage. Not the institution, the word. Semantics is what the Federal Marriage Amendment is all about.
Whether or not the FMA will permit states to have both heterosexual marriage and homosexual civic unions, there is strong case to be made that it will permit one-size-fits-all civic unions if the state abolishes civic "marriage."
After all, is there anything that requires a state to recognize the institution of marriage? Must a state recognize a couple's supposed marital status? Where is the list of legal incidents a state has to provide to the married? I doubt there is such a list, as states have previously been free to change the legal incidents of marriage at their will. Used to be that one couldn't rape their spouse, now you can. Divorce was difficult to get, now it is easy. And taxes, whoa boy, is there some guarantee that people can file their taxes as a married couple?
If a state abolishes "marriage" and establishes a same-sex permitting "civic union" law, how would the FMA apply to that state? Would it be unconstitutional to abolish marriage? If so, would we have some sort of minimal Federal Marriage Law requirements that states would have to abide by? If marriage were abolished, would the Supreme Court declare that certain aspects of civic unions were actually elements of a "marriage" even if a state claimed they were civic unions? Wouldn't this inevitably lead to a Federal Common Law of marriage?
Abolishing Marriage through the Courts
Massachusetts' state constitution has been interpreted by the state's Supreme Court to require that marriage rights be granted to both homosexual and heterosexual couples; mere civic unions for gays would not be sufficient to meet the Massachusetts Constitution's equal protection requirements. Imagine if the FMA were passed and the Massachusetts courts had to address the issue again.
Undoubtedly, the unequal treatment would still be repugnant to the equal protection measures of the Constitution of Massachusetts. However, Massachusetts courts would be forbidden from requiring that marriage rights be given equally to homosexuals. However, this would not prevent the Massachusetts courts from declaring that marriage itself must be abolished to correct the disparate treatment. The FMA prevents homosexuals from having the same privileges as heterosexuals. It does not prevent heterosexuals from having their privileges taken away to make them equal to homosexuals.
After "marriage" was abolished, there would be no constitutional issue in Massachusetts establishing an equal rights friendly "civic union" law.
How to Ignore a Constitutional Amendment
Imagine that the FMA has now passed, over the objections of several states. Rather than permit such an injustice, some of the protesting states abolish marriage within their borders. Over time, acceptance of same-sex unions grow as does the idea that civic unions are the proper purview of the state and marriages the purview of the various churches.
Undoing a constitutional amendment requires another constitutional amendment, which is very difficult to do. Rather than go through that process, as individual states become more same-sex friendly many would abolish marriage rather than work on amending the constitution. Ultimately, the FMA and civil marriage becomes irrelevant, quaint legal relics similar to the Third Amendment.
The Federal Benefits Question
Actually, marriage would not be entirely abolished. States would still have to permit vestigial "marriages" in order for heterosexual couples to receive various and sundry federal benefits. Marriage would come to be defined as the union of a man and woman for purposes of receiving federal benefits.
So-called defenders of the institution of marriage should be careful what they ask for.