The Second Amendment is naturally divided into two parts: its prefatory clause and its operative clause. The former does not limit the latter grammatically, but rather announces a purpose. The Amendment could be rephrased,“Because a well regulated Militia is necessary to the security of a free State, the right of the people to keep and bear Arms shall not be infringed.”

Next quote:

1. Operative Clause.

a. “Right of the People.” The first salient feature of the operative clause is that it codifies a “right of the people.”

The unamended Constitution and the Bill of Rights use the phrase “right of the people” two other times, in the First Amendment’s Assembly-and-Petition Clause and in the Fourth Amendment’s Search-and-Seizure Clause. The Ninth Amendment uses very similar terminology (“The enumeration in the Constitution, of certain rights, shall not be construed to deny or disparage others retained by the people”). All three of these instances unambiguously refer to individual rights, not “collective” rights, or rights that may be exercised only through participation in some corporate body.5

And,

As we will describe below, the “militia” in colonial America consisted of a subset of “the people”— those who were male, able bodied, and within a certain age range. Reading the Second Amendment as protecting only the right to “keep and bear Arms” in an organized militia therefore fits poorly with the operative clause’s description of the holder of that right as “the people.”

We start therefore with a strong presumption that the Second Amendment right is exercised individually and belongs to all Americans.

On the phrase "keep and bear arms":

....the most natural reading of “keep Arms” in the Second Amendment is to “have weapons.” ....At the time of the founding, as now, to “bear” meant to “carry.”

And,

c. Meaning of the Operative Clause. Putting all of these textual elements together, we find that they guarantee the individual right to possess and carry weapons in case of confrontation. This meaning is strongly confirmed by the historical background of the Second Amendment.

We look to this because it has always been widely understood that the Second Amendment, like the First and Fourth Amendments, codified a pre-existing right. The very text of the Second Amendment implicitly recognizes the pre-existence of the right and declares only that it “shall not be infringed.” As we said in United States v. Cruikshank, 92 U. S. 542, 553 (1876), “[t]his is not a right granted by the Constitution. Neither is it in any manner dependent upon that instrument for its existence. The Second amendment declares that it shall not be infringed.

It's not a right without limits.

Of course the right was not unlimited, just as the First Amendment’s right of free speech was not, see, e.g., United States v. Williams, 553 U. S. ___ (2008). Thus, we do not read the Second Amendment to protect the right of citizens to carry arms for any sort of confrontation, just as we do not read the First Amendment to protect the right of citizens to speak for any purpose.

The opinion discusses limitations on guns that people can carry and who can carry them:

Although we do not undertake an exhaustive historical analysis today of the full scope of the Second Amendment, nothing in our opinion should be taken to cast doubt on longstanding prohibitions on the possession of firearms by felons and the mentally ill, or laws forbidding the carrying of firearms in sensitive places such as schools and government buildings, or laws imposing conditions and qualifications on the commercial sale of arms.

On the DC handgun ban:

....the law totally bans handgun possession in the home. It also requires that any lawful firearm in the home be disassembled or bound by a trigger lock at all times, rendering it inoperable.

As the quotations earlier in this opinion demonstrate, the inherent right of self-defense has been central to the Second Amendment right. The handgun ban amounts to a prohibition of an entire class of “arms” that is overwhelmingly chosen by American society for that lawful purpose.

The prohibition extends, moreover, to the home, where the need for defense of self, family, and property is most acute. Under any of the standards of scrutiny that we have applied to enumerated constitutional rights,27 banning from the home “the most preferred firearm in the nation to ‘keep’ and use for protection of one’s home and family,” 478 F. 3d, at 400, would fail constitutional muster.

Also,

We must also address the District’s requirement (as applied to respondent’s handgun) that firearms in the home be rendered and kept inoperable at all times. This makes it impossible for citizens to use them for the core lawful purpose of self-defense and is hence unconstitutional.

In a later section, here's an interesting paragraph:

A constitutional guarantee subject to future judges’ assessments of its usefulness is no constitutional guarantee at all. Constitutional rights are enshrined with the scope they were understood to have when the people adopted them, whether or not future legislatures or (yes) even future judges think that scope too broad.

Finally, the ruling:

In sum, we hold that the District’s ban on handgun possession in the home violates the Second Amendment, as does its prohibition against rendering any lawful firearm in the home operable for the purpose of immediate self-defense. Assuming that Heller is not disqualified from the exercise of Second Amendment rights, the District must permit him to register his handgun and must issue him a license to carry it in the home.

The final paragraphs address the problem of handgun violence, to which the Court says it is sensitive. But, it says:

The Constitution leaves the District of Columbia a variety of tools for combating that problem, including some measures regulating handguns, see supra, at 54–55, and n. 26. But the enshrinement of constitutional rights necessarily takes certain policy choices off the table. These include the absolute prohibition of handguns held and used for self-defense in the home. Undoubtedly some think that the Second Amendment is outmoded in a society where our standing army is the pride of our Nation, where well-trained police forces provide personal security, and where gun violence is a serious problem. That is perhaps debatable, but what is not debatable is that it is not the role of this Court to pronounce the Second Amendment extinct.

That last line was great. That's a wrap for the majority opinion.

***

DC Handgun Ban Opinion: 10:00 AM Thursday

The Supreme Court will release three opinions at 10 am Thursday, including D.C. v. Heller, deciding the constitutionality of D.C.'s handgun ban and settling the question of whether the Second Amendment conveys an individual right to bear arms. (Background here and here.)

Scotus Blog will be live-blogging again here and will have the fastest announcement of the decision and link to the opinion.

Update: Here's a new thread to discuss reactions to today's decision.