The doctrine of States' Rights took a heavy blow from the Supreme Court's decision in McDonald v. Chicago this week, and it was the court's right wing that delivered it.
To understand what the Court did, first we consider the Second Amendment.
A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed.
We must now note that this amendment refers to "the people", and ask the question "shall not be infringed" by whom? In this context we shall consider the 1833 case of Barron v. Baltimore, an early Fifth Amendment case on eminent domain. The Fifth Amendment, with emphasis added to the parts relevant to this discussion, states that:
No person shall be held to answer for a capital, or otherwise infamous crime, unless on a presentment or indictment of a Grand Jury, except in cases arising in the land or naval forces, or in the Militia, when in actual service in time of War or public danger; nor shall any person be subject for the same offense to be twice put in jeopardy of life or limb; nor shall be compelled in any criminal case to be a witness against himself, nor be deprived of life, liberty, or property, without due process of law; nor shall private property be taken for public use, without just compensation.
In Barron v. Baltimore, the Supreme Court unanimously held that the entire Bill of Rights only restrained acts of Congress. By the Barron decision, when the law says "shall not be infringed" it means "by Congress". The states can do what they want. The notion that the states can freely violate human rights is backed up by the Tenth Amendment:
The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.
The word "respectively" means precisely that the States have priority over the people. This is a strong foundation for the most expansive notion of States' Rights, of powerful, independent State governments, which lasted until the adoption of the Fourteenth Amendment after the Civil War. The most relevant part of the Fourteenth Amendment states:
No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws.
The Fourteenth Amendment is widely seen as applying the Bill of Rights onto the States through the "due process" clause which requires trial for a crime before a person's "life, liberty, or property" can be removed. The majority opinion in the 1925 case Gitlow v. New York started off by simply declaring, without further explanation, "that freedom of speech and of the press are among the personal rights and liberties protected by the due process clause of the Fourteenth Amendment from impairment by the States." This is a key precedent that separates the doctrine of States' Rights from the modern course of law followed by 20th century liberals. States' Rights proponents would deny that the clause has this effect as simply as the Gitlow court said that it did.
The Fourteenth Amendment could also incorporate the Bill of Rights through the "privileges or immunities" clause. If, however, we would apply a more restrained reading based on the words "of citizens" then this clause would protect little more than the right to vote. Such a limited reading is made in the Slaughterhouse Cases of 1872 in which the Supreme Court held that "the first clause of the fourteenth article was primarily intended to confer citizenship on the negro race".
If we accepted such restrained readings of both of these key clauses of the Fourteenth Amendment in the way that States' Rights supporters do, the Barron decision would still be valid. And by this restrained reading of the Fourteenth Amendment, it would not apply the Second Amendment to the states and so States' Rights supporters should see no Constitutional problem with Chicago's anti-handgun law.
Even the right-wing Federalist Society members of the Supreme Court do not consider the Fourteenth Amendment so restrained. Consider one recent Supreme Court case, Kelo v. New London in 2005, which justified the city' seizure of a private citizen's home based on the existence of a development plan. The right-wing dissent took for granted that the Fifth Amendment applies to the states in finding a right of the people not to have their properties taken by the state except for public use.
And we now come to McDonald v. Chicago. By the doctrine of States' Rights and a limited Fourteenth Amendment, the Second Amendment would restrain only Congress. By this doctrine, the states should have the power to limit firearms ownership. Yet it is the court's Federalist right wing which applies the Second Amendment onto the states. Samuel Alito's opinion specifically invokes the 20th century interpretation of the Due Process clause. Only Clarence Thomas's concurrence rejects this interpretation of the Due Process clause, instead rejecting the Slaughterhouse Cases to find support for the right to bear arms in the Privileges and Immunities clause.
I would expect the Republican Party to be splitting on this issue in a loud and visible way, but principles have given way to ideology. Ideologues in both parties have their ideas of what they want, will use any reading of the law to get court rulings supporting their desires, and will not apply the law consistently to all things. The Republican right will use an expansive Fourteenth Amendment to place gun ownership and private property above the authority of the states, but will gladly ignore the entire remainder of the Constitution. The Democratic left will use an expansive Fourteenth Amendment to secure freedom of speech, assembly, and abortion, and the separation of church and state, but will not recognize the right to bear arms as an equally protected human right. And so goes American politics.