with whom Justice Marshall and Justice Blackmun join, concurring.
I agree with the substantive standard announced by the Court today, imposing liability when a public-official defend*821ant “knew or should have known” of the constitutionally vio-lative effect of his actions. Ante, at 815, 819. This standard would not allow the official who actually knows that he was violating the law to escape liability for his actions, even if he could not “reasonably have been expected” to know what he actually did know. Ante, at 819, n. 33. Thus the clever and unusually well-informed violator of constitutional rights will not evade just punishment for his crimes. I also agree that this standard applies “across the board,” to all “government officials performing discretionary functions.” Ante, at 818. I write separately only to note that given this standard, it seems inescapable to me that some measure of discovery may sometimes be required to determine exactly what a public-official defendant did “know” at the time of his actions. In this respect the issue before us is very similar to that addressed in Herbert v. Lando, 441 U. S. 153 (1979), in which the Court observed that “[t]o erect an impenetrable barrier to the plaintiff’s use of such evidence on his side of the case is a matter of some substance, particularly when defendants themselves are prone to assert their goo[d fjaith . . . .” Id., at 170. Of course, as the Court has already noted, ante, at 818-819, summary judgment will be readily available to public-official defendants whenever the state of the law was so ambiguous at the time of the alleged violation that it could not have been “known” then, and thus liability could not ensue. In my view, summary judgment will also be readily available whenever the plaintiff cannot prove, as a threshold matter, .that a violation of his constitutional rights actually occurred. I see no reason why discovery of defendants’ “knowledge” should not be deferred by the trial judge pending decision of any motion of defendants for summary judgment on grounds such as these. Cf. Herbert v. Lando, supra, at 180, n. 4 (Powell, J., concurring).
Justice Brennan,Justice White, Justice Marshall, and Justice Blackmun, concurring.
We join the Court’s opinion but, having dissented in Nixon *822v. Fitzgerald, ante, p. 731, we disassociate ourselves from any implication in the Court’s opinion in the present case that Nixon v. Fitzgerald was correctly decided.
Justice Rehnquist,concurring.
At such time as a majority of the Court is willing to reexamine our holding in Butz v. Economou, 438 U. S. 478 (1978), I shall join in that undertaking with alacrity. But until that time comes, I agree that the Court’s opinion in this case properly disposes of the issues presented, and I therefore join it.