Pretty much the question as asked. If a state has created an amendment such as blocking gay marriage, legalizing drugs, or assisted suicide, could a Supreme Court of the US overrule the amendment and remove it?
Short answer: yes. Not going into each specific example, the Supreme Court has the authority to review State legislation if there is a federal question. Most of the rights enumerated in the Constitution have been applied to the states. If an act violates a federal const. right, then the court may rule state legislation or action unconstitutional.
Possibly, if it violates some of the limits of the federal Constitution that are applicable to state governments. To take a trivial example, the federal Constitution guarantees each state a republican form of government, so an attempt to make Ted Kennedy the King of Massachusetts by state constitutional amendment would be struck down.
Take it this way:
If the Assistant Director in Charge of Creating Red Tape of the State Division of Obfuscation and Sesquipedalian Rhetoric creates a set of regulations, they must conform to the statute law authorizing the adoption of regulations in order to be valid. He has no right in and of himself to make rules that others must follow; his only authority rests in the power given him by the state legislature by statute law to do so.
If the state legislature passes a statute, on this or any other topic, that statute, in content and procedurally, must conform to the State Constitution; the legislature has no right to adopt a statute on a given topic unless it’s empowered to do so by the will of the people as expressed in the state constitution.
Likewise the Federal bureaucracy and Congress, as regards Federal regulations and statutes.
Now the kicker is this – we are a union of 50 sovereign states, which have delegated certain powers to the Federal government and agreed that the U.S. Constitution, and laws and treaties adopted in conformity with it, constitute the supreme law of the land.
If a State Legislature amends the State Constitution in a manner that does not conform to the provisions of the U.S. Constitution, it’s breaking the supreme law of the land, the U.S. Constitution, in doing so. For example, a State may not set up a given Christian denomination as the official state religion, or institute a poll tax, or abolish jury trials altogether.
Now, if a State should decide to do something of this sort, what’s the recourse of the person injured by its act? Presumably, to act as though the law is not valid, or to challenge it by suit, as may be appropriate given the terms of the act. Who decides this? Well, it’s “a Federal question” – i.e., something affecting rights and powers specified in the U.S. Constitution. Therefore, the Federal courts have the right to make a decision relative to it. And if the issue is appealed, the final arbiter of such an appeal is SCOTUS.
But just to note, the 3 examples given in the OP (SSM, drugs, suicide) do not have an established federal constitutional basis, so it is not at all clear that the SCotUS WOULD rule them unconsitutional. In do so, the Supremes would be adding a new interpretation to existing constitutional law.
Not to turn this into GD, but isn’t that what happened with Loving v. Virginia?
and using the Court’s decision on that, in concert with Lawrence et al vs. Texas
The new interpretation of Constitutional law would be based on these precedents for shooting down a state amendment banning gay marriage. (I would reckon).
So the bigger question is, for example using Loving V Virginia, did any of the states barring miscegenation have a state amendment prohibiting it that caused it to be overturned as unconstitutional?
True. The Federal Courts up to and including SCotUS would have to include in their considerations first of all whether there are federal constitutional-law issues at play in the case, and if so, how do they apply here. They can’t just say “5 of us think SSM should be allowed across the land”, they have to say something to the effect of “5 of us think this SSM ban violates equal protection/due process/privacy/full-faith-and-credit/whatever we could find in the penumbrae of the constitution, and here’s 300 pages of cites as to how we came to that conclusion; figure out another way or let it happen”.
One example, particularly appropriate since it’s from Colorado and I’m guessing the OP may have been inspired in part by the potential brouhaha should Colorado pass its electoral vote amendment, is Romer v Evans, in which Colorado’s anti-gay Amendment 2 was struck down by SCOTUS on federal constitutional grounds (specifically as a violation of the 14th Amendment’s Equal Protection clause).
In Baker v Carr (1962) the Supreme Court threw out a whole chunk of Article 2 of the Tennessee constitution when it ruled that “little Federal” methods of apportioning state legislatures violated the 14th Amendment. In doing so, the SCOTUS pretty much required every state but Nebraska to reorganize their legislatures.
But remember that, at least in the question of individual rights, the federal constitution is a floor, not a ceiling. States can adopt greater protections, and have increasingly done so since the late Justice Brennan’s enormously influential 1977 article, “State Constitutions and the Protection of Individual Rights,” 90 Harv. L. Rev. 489. Brennan, the intellectual architect of much of the Warren Court’s jurisprudence, recognized that state supreme courts could interpret their own constitutions quite expansively - and those decisions would not be reviewable by the federal court system, so long as the decision didn’t end up violating a federal right in the process. So, for example, even after SCOTUS’s 1985 Bowers v. Hardwick decision held that sodomy laws didn’t violate the federal constitution, several state supreme courts invalidated sodomy laws based on state constitutional privacy guarantees.
As I recall, some states courts have interpreted state constitutional rights provisions much more expansively than their federal counterparts, even when they’re phrased almost identically. That has frustrated many conservatives, who claim that instead of fighting one liberal court, they’re fighting 50.