The jurisprudential weaknesses of the majority opinion authored by Justice Antonin Scalia are beyond the scope of this blog posting (I may elaborate later), but the actual holding of the case, and the true effect of the opinion, need to be explained more fully than has been covered in the popular press to date.
Although the Supreme Court held that the Second Amendment's "right of the People to keep and bear arms" was an individual right and not a right of the states to maintain militias, and held that a ban on handguns violated the Second Amendment, the holding of the case was still relatively narrow because the law in question was an ordinance of the District of Columbia and not a statute enacted by one of the states.
The District of Columbia is a peculiar place, constitutionally speaking, because it is governed by Congress in accordance with Article I, Section 8, clause 17, of the Constitution, and is not a "state" (or a part of any state) within the meaning of the Constitution. That peculiarity is important because, technically speaking, the Bill of Rights (the first ten amendments to the Constitution, including the 2nd Amendment) are binding only on the federal government and not the states. The fundamental freedoms guaranteed by the Bill of Rights apply to the states only through the 14th Amendment's guarantee of due process of law. So (for example), a state law that violates the right to freedom speech is not, technically speaking a violation of the 1st Amendment, which only applies to the federal government, but is a violation of the 14th Amendment.
In the Heller case, Scalia's opinion specifically recognized that the question of whether 2nd Amendment rights were "incorporated" into the 14th Amendment (and so applicable to the states) was not before the court, and that the court had previously ruled that the 2nd Amendment did not apply to the states. This is explicit in footnote 23, discussing a statement in United States v. Cruikshank, 92 U. S. 542, 553 (1876) that stated that the 2nd Amendment only limited the power of Congress, and was not incorporated into the 14th Amendment:
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. Our later decisions in Presser v. Illinois, 116 U. S. 252, 265 (1886) and Miller v. Texas, 153 U. S. 535, 538 (1894), reaffirmed that the Second Amendment applies only to the Federal Government.Slip Opinion, page 48, note 23 (emphasis added).
This footnote says (and suggests) several things.
First, the question of whether the 2nd Amendment applies to state legislation was not before the court in Heller and was not decided, and so remains an open question.
Second, the Supreme has in past decisions (Presser and Miller) affirmed that the 2nd Amendment applies only the federal government.
Third, that Cruikshank (and perhaps later decisions) did not interpret the 14th Amendment in the same way that later decisions interpreted that amendment.
The third point, combined with Scalia's citations to statements made in Congress during the debates over the 14th Amendment that the 2nd Amendment represented a "fundamental right" enjoyed by American citizens (see pages 41-47), are clear signals that Scalia believes the 2nd Amendment does apply to the states, and is just waiting for right case in which to make that decision.