1. Heller recognized a right to keep and bear arms in self-defense, which logically presupposes some legal right to self-defense. Why would the Constitution let you keep an object for a certain purpose, when all use of the object for that purpose could be outlawed?
2. Heller often talks of a "right to self-defense" in contexts that suggest it is of constitutional stature, e.g., "That of the nine state constitutional protections for the right to bear arms enacted immediately after 1789 at least seven unequivocally protected an individual citizen's right to self-defense is strong evidence that that is how the founding generation conceived of the right."
3. I suppose that a right to keep and bear arms in self-defense could coexist with a regime that allowed people only a right to self-defense using arms, and that banned unarmed self-defense, or self-defense with weapons that might not qualify as "arms" for Second Amendment purposes. But that wouldn't make a lot of sense: Why would you have a right to defend yourself — lethally, if necessary — using the most lethal weapons, and not using less lethal means? Sometimes the legal answer to some questions is "because that's the way we've always done things, even if you think that's illogical," but that answer can't work here, because tradition is on the side of a right to self-defense using whatever means come to hand.
4. But can an opinion by Justice Scalia, no fan of unenumerated rights, be read as recognizing such a right? Well, it does seem to read that way on its face; and beyond that, Justice Scalia has signalled an openness both to unenumerated rights when they have been broadly recognized for hundreds of years, and to this right in particular. See Montana v. Egelhoff, 518 U.S. 37, 56 (1996) (four-Justice plurality authored by Justice Scalia) (suggesting that "the right to have a jury consider self-defense evidence" may be "fundamental" and supported by the "historical record"; such a right would make little sense if self-defense could be abolished as a defense).
[UPDATE:] 5. Likewise, even the narrowest test that the Court has recently announced for recognizing unenumerated rights — the Washington v. Glucksberg test, which focuses on whether a right is important and broadly recognized throughout America and throughout American history — cuts in favor of recognizing a right to self-defense. Now if one rejects unenumerated rights under the Due Process Clause, under the Privileges or Immunities Clause, and under the Ninth Amendment, then one would just be left with the right's being implied by the Second Amendment. (My sense is that nearly all Justices and nearly all major commentators accept some implicit rights, such as the right to expressive association that is seen as implicit in the First Amendment. The controversy arises when the implication gets too tenuous, and when the right is really being urged as an independently secured, albeit not expressly enumerated, right.)
6. At least some lower court judges — including some Reagan and Bush appointees — have shown a willingness to recognize a constitutional right to self-defense, even before the Second Amendment was recognized an individual right. Compare, e.g., Rowe v. DeBruyn, 17 F.3d 1047, 1054-56 (7th Cir. 1994) (Ripple, J., dissenting); id. at 1047 n.** (Cudahy, Flaum, Ripple, and Rovner, JJ., supporting rehearing en banc); DeCamp v. N.J. Dep't of Corr., 902 A.2d 357, 361--62 (N.J. Super. Ct. App. Div. 2006) (endorsing Judge Ripple's position and concluding that prisoners have self-defense rights, though without explicitly deciding whether those are federal constitutional rights or only state law rights); Isaac v. Engle, 646 F.2d 1129 (6th Cir. 1980) (en banc) (Merritt, J., dissenting), rev'd on other grounds, 456 U.S. 107 (1982) with Rowe, 17 F.3d at 1052-53 (7th Cir. 1994) (rejecting a constitutional right to self-defense generally, though the case involved only prisoner rights); White v. Arn, 788 F.2d 338, 347 (6th Cir. 1986) (rejecting a constitutional right to self-defense generally, though the only issue in the case was whether the defendant could be required to prove self-defense by a preponderance of the evidence, rather than requiring the prosecution to disprove self-defense beyond a reasonable doubt).
7. Likewise, at least two state courts have expressly read a state constitutional right to bear arms in self-defense provision as supporting a right to self-defense, at least with the constitutionally protected arms (though for the reasons mentioned in item 2, I don't see how the right would be so limited). See McKellar v. Mason, 159 So. 2d 700, 702 (La. Ct. App. 1964); State ex rel. City of Princeton v. Buckner, 377 S.E.2d 139, 142--44 (W. Va. 1988).
8. If one counts all the states that have a right to bear arms for individual self-defense in the state constitution together with all the states that have a right to defend life expressly mentioned in the state constitution (and many state courts have indeed read such rights to defend life and property as securing constitutionally protected rights), one gets 44 of the 50 states — an important marker of the breadth of self-defense as a constitutionally secured right, and not just a common-law right. See generally Volokh, State Constitutional Rights of Self-Defense and Defense of Property, 11 Tex. Rev. of L. & Pol. 399 (2007); see also this earlier post and this one.
None of these, standing alone, would be dispositive evidence that the courts are likely to recognize a constitutional right to self-defense in the wake of Heller. But put together, it seems to me they point strongly in that direction.
9. I should note, though, that this surely doesn't mean a constitutional right to use deadly force in all circumstances in which one is defending oneself. Historical limitations on this right — either broadly accepted, or at least accepted by a substantial minority of states — are likely to be upheld, especially if history and tradition is a large part of the basis for recognizing the right in the first place.
Thus, a rule that one can only use deadly force to defend oneself against threats of death, serious bodily injury, rape, kidnapping, and a few other very serious threats would likely be constitutional (even though many states also allow use of deadly force to defend against robbery and in some situations burglary). Likewise, the "duty to retreat," which is to say the principle that deadly force can only be used in self-defense if it's genuinely necessary, in that no safe avenue of retreat is available, is likely to be constitutional, too, because it has long been recognized in at least a substantial minority of states. There may be other examples as well. My point is that a federal constitutional right to self-defense likely exists, especially in the wake of Heller. But it is not unlimited, and is likely to be strongest precisely where there's a broad and deep common-law and statutory tradition of recognizing such a right.
[UPDATE:] This might mean that the constitutional right to self-defense is only rarely relevant to a judicial decision. But that might simply reflect how broadly and deeply accepted the right is. If legislatures and state courts consistently honor a constitutional right to self-defense — because it's so deeply embedded in American moral thinking and the American legal tradition — then indeed there'll almost never be a case in which a governmental decision is struck down based on a constitutional right to self-defense. Nothing inherently wrong with that.