Prof. Keller on Heller, Justice Breyer and culture wars
He posts over at The Volokh Conspiracy. Interesting point. In an earlier school voucher case, Breyer considered a potential harm to a constitutional interest (that controversial religions might created funded schools, that the public would demand that measures be taken against them, and that that would lead to entanglement of church and state, even if the voucher system itself did not) sufficient to vote to strike a law. No need for opponents of the law to prove probability here; the presumption is that this will occur, or at least that possibility of this is enough.
In Heller, it's the other way around. Instead of guessing/projecting/speculating in favor of the constitutional interest, Breyer does so in favor of considerations weighing against the interest. He notes that DC's crime rate rose after the ban, but then coincidence does not prove causation, and there is no way to know what the crime rate would be without the ban. That'd sound like a reason to strike the ban: constitutional guarantee, and people proposing a restriction cannot show, one way or the other, that the restriction is beneficial or not. But now he says that call is up to the legislature, its enactment and judgment that things are good is presumed correct unless the party supporting the right can disprove it: "the question here is whether they [the arguments] are strong enough to destroy judicial confidence in the reasonableness of a legislature that rejects them. "