What will happen to these couples if same-sex marriage is banned in the future? Will they continue to be married in the eyes of the law? Will the ban be made retroactive? Is that even legally possible? If not, will there be a special class of same-sex couples who will be legally married, while others cannot?The bottom line up front: No one knows for sure. No one can say with absolute certainty. Most likely, it will eventually end up on the US Supreme Court's doorstep for determination. I can just imagine the intense frustration that must cause for both sides of the aisle in contemplating the legal uncertainties of the future.
I will try to focus specifically on this question: "Can the ban be made retroactive - is that even legally possible?" For the purposes of argument, I assumed we were talking about a federal constitutional amendment banning gay marriage, rather than a state constitutional amendment.
In trying to answer that question, I started by trying to prove it would not be possible. That for those couples who legally marry between now and the time an amendment is passed, the legal effect of their marriage can not be undone retroactively. I looked for support in the text of the US Constitution concerning ex post facto laws, bills of attainder, and impairing contracts.
Article 1, Section 9, Clause 3 states "No Bill of Attainder or ex post facto Law shall be passed," and shortly thereafter Section 10 states: "No State shall... pass any Bill of Attainder, ex post facto Law, or Law impairing the Obligation of Contracts"
An Ex Post Facto law is a law passed after the occurrence of an event or action which retrospectively changes the legal consequences of the event or action. A Bill of Attainder is a legislative act that singles out an individual or group for punishment without a trial. A law impairing the Obligation of Contracts would be a law that retroactively releases one party to a contract from their obligations under the contract. Section 9 made them prohibited for the federal government, and Section 10 made them prohibited for the states. Note that with regard to impairing the obligation of contracts, it is prohibited by the states but not by the federal government. Before we look at how those clauses might prevent a constitutional amendment from being applied retroactively, however, we need an example of what such a constitutional amendment might look like. Since we do not know whether or not such an amendment will ever be passed, and exactly what it will say, the following example is just as arbitrary as any other:
"Marriage in the United States shall consist only of the union of a man and a woman. Neither the United States nor any State shall recognize or grant to any unmarried person the legal rights or status of a spouse."Such an amendment would be designed to first define what marriage is in the United States, then proceed to prohibit the federal government and the state governments from recognizing or giving legal rights or legal status to anyone who is "not married." Since you are only married if you are a man and a woman, gay and lesbian couples fall into the "not married" group.
Returning to the constitutional safeguards against retroactive laws, we'll need to look at them individually. Please remember that in the context of what follows, we are only talking about the issue of whether or not it is legally possible to make a Gay Marriage ban retroactive:
1. Ex Post Facto. Arguments in favor of declaring an amendment unconstitutional might try to draw support from the Ex Post Facto clause. It might be argued that since the amendment was passed after the marriages, it can not be retroactively applied to undo the legal rights granted to the marriages. Unfortunately, the US Constitution did not clearly define what an Ex Post Facto law was, and the US Supreme Court interpreted the "words and intent" of the Ex Post Fact clause as encompassing "[e]very law that changes the punishment, and inflicts a greater punishment, than the law annexed to the crime, when committed." (Calder v. Bull, 3 U.S. 386, decided 1798). I shepardized the case and as you can imagine, there is a long line of cases after Calder but a sampling indicated that they contemplated the use of the Ex Post Facto clause with regard to
criminal laws, not civil laws. In Calder, the majority opinion stated that the proscription against ex post facto laws was derived from English common law well known to the Framers, and set out four categories of ex post facto criminal laws: "1st. Every law that makes an action done before the passing of the law, and which was innocent when done, criminal; and punishes such action. 2d. Every law that aggravates a crime, or makes it greater than it was, when committed. 3d. Every law that changes the punishment, and inflicts a greater punishment, than the law annexed to the crime, when committed. 4th. Every law that alters the legal rules of evidence, and receives less, or different, testimony, than the law required at the time of the commission of the offence, in order to convict the offender." In the recent case Carmel v. Texas (529 U.S. 513, decided 2000), the Supreme Court acknowledged that it has repeatedly endorsed this understanding. So, ultimately, the problem with trying to declare an Anti-Gay marriage amendment unconstitutional on the grounds of the Ex Post Facto clause may run into the problem that historically, the Supreme Court has only interpreted it to prohibit
criminal Ex Post Facto laws.
2. Bills of Attainder. Arguments in favor of declaring an amendment unconstitutional might try to draw support from this clause, which prohibits a legislature from singling out an individual or group for punishment without a trial. However, simliar to the way the Ex Post Facto clause operates, Bills of Attainder were designed to prevent the legislature from usurping the power of the courts to adjudicate criminal trials, not civil matters. Someone might try to argue that gays and lesbians are being "punished" by an amendment but that is not an accurate use of the term punishment within the context of Bills of Attainder. The drafting of the clause probably borrowed heavily from what happened in England in the late 17th Century; Sir John Fenwick was charged with high treason, but could not be convicted without the testimony of two witnesses. Parliament passed a bill of attainder making the two-witness rule inapplicable, and Fenwick was forthwith convicted on the testimony of only one witness. So we see that the history behind the Bill of Attainder clause has its roots in preventing the legislature from usurping judicial power and affecting the outcomes of
criminal matters. According to U.S. v. Brown (381 U.S. 437, decided 1965), it was intended as a "a general safeguard against legislative exercise of the judicial function or more simply - trial by legislature." And as much as I may personally dislike the opinions of the current Chief Justice of the Supreme Court, "These clauses of the Constitution are not of the broad, general nature of the Due Process Clause, but refer to rather precise legal terms which had a meaning under English law at the time the Constitution was adopted. A bill of attainder was a legislative act that singled out one or more persons and imposed punishment on them, without benefit of trial. Such actions were regarded as odious by the framers of the Constitution because it was the traditional role of a court, judging an individual case, to impose punishment." (William H. Rehnquist, in
The Supreme Court, page 166).
3. Impairing the obligation of contracts. When two people marry, is commonly held that the marriage is in and of itself a contract. Arguments in favor of declaring an amendment unconstitutional might try to draw support from this clause, on the grounds that the amendment would render the obligation of contracts between two married persons (gay or lesbian) moot and unenforceable. There are at least two problems with this, however. First, the Amendment in question above would not prohibit gay and lesbian couples from being bound to each other by whatever contracts they have with each other. The text of the marriage amendment only prohibits the federal and state governments from recognizing or granting to any "unmarried person" the legal rights or status of a spouse. So while the law would prevent a State Court from allowing a gay or lesbian couple to sue their employer for denial of spousal benefits, it would not prevent a gay or lesbian individual from suing their partner over any obligations they might owe each other from entering into a contract. Secondly, because the Obligation of Contracts clause under Article 1 only binds the state governments and not the federal government, it would really only apply to state constitutional amendments, not federal constitutional amendments. Since we are talking about a federal constitutional amendment here, it probably renders the Obligation of Contracts argument moot.
Coming full circle, it is therefore my opinion that it
is possible that a constitutional amendment could be passed, effectively defeating gay marriage rights with regard to the benefits of marriage, that could operate to retroactively take away the benefits being granted to gays and lesbians being married in the here and now, unless someone can think of a way to work with other parts of the Constitution. My understanding of the original poster's question went to the heart of this issue, and my answer is "unknown." None of what I've said should be construed as proving the issue in either direction - my overall point is that based on what I can gather from the US Constitution and its interpretation, I believe it wouldn't necessarily preclude a constitutional amendment cleverly designed to undo gay and lesbian spousal rights and benefits. Of course, I could be wrong. And ultimately, it will be up the US Supreme Court to carefully parse through and decide this issue.
At this point, before clicking the "submit post" button, I feel like I should add my own two cents on the anti-marriage amendment issue (disclaimer: what follows is purely my own opinion). I am
against any such amendment. Many different people see this issue on different levels and in different terms, and I can respect the opinion of people who feel that gay marriages should not be considered marriages, but I see this as fundamentally a discrimination issue. If we as a nation go forward with and ratify an amendment like the one in question, we will be doing something we have never done before: actively enshrining discrimination into our Constitution. I'm sure there are others who see it differently, but that is what I believe.

(edited: spelling and grammar)