More importantly, If a State can selectively restrict the 2nd Amendment, what prevents them from selectively restricting other rights guaranteed to us by our Constitution. Could the 1st Amendment be restricted, or any other by a State?
YES, at one time a State could (and many did) restrict your 1st Amendment Rights
remember, originally states COULD restrict all your basic rights.
The COTUS's Bill of Rights was simply a promise that the Federal Government would never restrict those rights.
There have been rulings in the past where SCOTUS upheld a state's right to do things the Feds could not (Barron v. Baltimore...a state can ignore you 5th amendment rights to protection against having items taken without just compenstion, like taking land for a road without paying you for it. United States v. Cruikshank found that the First Amendment right to assembly "was not intended to limit the powers of the State governments in respect to their own citizens")
This is where the 14th amendment comes in
"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."
Exactly what that means is of course open to debate. As time passes, SCOTUS has ruled again and again that when a protection is listed in the bill of rights, it is a 'liberty' they cannot be denied.
This function has been termed 'incorporation'
It has been done bit by bit so far, either on an amendment by amendment basis, or sometimes by part-of-amendment by part-of-amendment
Example:
First Amendment
Guarantee against establishment of religion = Everson v. Board of Education
Guarantee of free exercise of religion = Cantwell v. Connecticut
Guarantee of freedom of speech = Gitlow v. New York
Guarantee of freedom of the press = Near v. Minnesota
Guarantee of freedom of assembly = DeJonge v. Oregon
Right to petition for redress of grievances & Guarantee of freedom of expressive association have not been specifically incorporated, but have been mentioned in passing in important cases and treated as if they were incorporated
So basically eventually the whole of the First Amendment has been Incorporated, and State Governments must obey it.
Swinging back a little...
United States v. Cruikshank found that the First Amendment right to assembly "was not intended to limit the powers of the State governments in respect to their own citizens" and that the Second Amendment "has no other effect than to restrict the powers of the national government."
This has often been cited as legal precident in allowing states to ban guns.
However this ruling was made AFTER the 14th amendment was in place. You will note that in Cruikshank SCOTUS says 'First Amendment to assemble is NOT enforcable on the state, even with the 14th Amendment' but in DeJonge v. Oregon SCOTUS overturns that half of Cruikshank.
So the question becomes, if A and B are deemed acceptable by SCOTUS for reason X...but then SCOTUS later says, regarding A only, that Reason X is flawed...where does that leave B?
It seems to me that even though DeJonge v. Oregon only addressed Free Assembly, the fact that they found US v Cruikshank to be wrong on it's reasoning means that it is wrong on whatever other aspects of law are arrived at by that same reasoning.
Scotomayor, our newest SCOTUS Justice thinks just the opposite, that only half of Cruikshank has been struck down, and hence state gun bans are totally Constitutional, even in light of the 14th and 2nd Amendments.
However, in the recent Heller ruling the following was said
"With respect to Cruikshank's continuing validity on incorporation, a question not presented by this case, we note that Cruikshank also said that the First Amendment did not apply against the States and did not engage in the sort of Fourteenth Amendment inquiry required by our later cases"
This is believed by some to be a 'trail of crumbs' left by Scallia explaining how we should go about incorporating the 2nd. We should argue that the Cruikshank case reached it's conclusion about the 1st and 2nd amendment using the same legal reasoning. Thanks to a later case showing that reasoning to be wrong, ALL of Cruikshank falls down...not just half.
... well... it doesn't really mean what it says. 
