So holds a unanimous Supreme Court (in an opinion by Justice Ginsburg) in this morning’s Wood v. Moss decision:

This case concerns a charge that two Secret Service agents, in carrying out their responsibility to protect the President, engaged in unconstitutional viewpoint-based discrimination. The episode in suit occurred in Jacksonville, Oregon, on the evening of October 14, 2004. President George W. Bush, campaigning in the area for a second term, was scheduled to spend the evening at a cottage in Jacksonville. With permission from local law enforcement officials, two groups assembled on opposite sides of the street on which the President’s motorcade was to travel to reach the cottage. One group supported the President, the other opposed him.
The President made a last-minute decision to stop in town for dinner before completing the drive to the cottage. His motorcade therefore turned from the planned route and proceeded to the outdoor patio dining area of the Jacksonville Inn’s restaurant. Learning of the route change, the protesters moved down the sidewalk to the area in front of the Inn. The President’s supporters remained across the street and about a half block away from the Inn. At the direction of the Secret Service agents, state and local police cleared the block on which the Inn was located and moved the protesters some two blocks away to a street beyond handgun or explosive reach of the President. The move placed the protesters a block farther away from the Inn than the supporters.
Officials are sheltered from suit, under a doctrine known as qualified immunity, when their conduct “does not violate clearly established … constitutional rights” a reasonable official, similarly situated, would have comprehended. The First Amendment, our precedent makes plain, disfavors viewpoint-based discrimination. But safeguarding the President is also of overwhelming importance in our constitutional system. Faced with the President’s sudden decision to stop for dinner, the Secret Service agents had to cope with a security situation not earlier anticipated. No decision of this Court so much as hinted that their on-the-spot action was unlawful because they failed to keep the protesters and supporters, throughout the episode, equidistant from the President.
The United States Court of Appeals for the Ninth Circuit ruled otherwise. It found dispositive of the agents’ motion to dismiss “the considerable disparity in the distance each group was allowed to stand from the Presiden[t].” Because no “clearly established law” so controlled the agents’ response to the motorcade’s detour, we reverse the Ninth Circuit’s judgment….
The protesters assert that it violated clearly established First Amendment law to deny them “equal access to the President” during his dinner at the Inn and subsequent drive to the cottage. The Court of Appeals agreed, holding that the agents violated clearly established law by moving the protesters to a location that “was in relevant ways not comparable to the place where the pro-Bush group was allowed to remain.” The Ninth Circuit did not deny that security concerns justified “mov[ing] the anti-Bush protesters somewhere.” But, the court determined, no reason was shown for “the considerable disparity in the distance each group was allowed to stand from the Presidential party.” The agents thus offended the First Amendment, in the Court of Appeals’ view, because their directions to the local officers placed the protesters at a “comparativ[e] disadvantag[e] in expressing their views” to the President.
No decision of which we are aware, however, would alert Secret Service agents engaged in crowd control that they bear a First Amendment obligation “to ensure that groups with different viewpoints are at comparable locations at all times.” Nor would the maintenance of equal access make sense in the situation the agents confronted.
Recall that at the protesters’ location on the north side of California Street they faced an alley giving them a direct line of sight to the outdoor patio where the President stopped to dine. The first move, to the corner of Fourth and California Streets, proved no solution, for there, only a parking lot stood between the protesters and the patio. True, at both locations, a six-foot wooden fence and an unspecified number of local police officers impeded access to the President. Even so, 200 to 300 protesters were within weapons range, and had a largely unobstructed view, of the President’s location. See Tr. of Oral Arg. 41 (counsel for respondents acknowledged that “in hindsight, you could … conclude” that “proximity [of the protesters to the President] alone … is enough to create a security [risk]”). See also Eggen & Fletcher, FBI: Grenade Was a Threat to Bush, Washington Post, May 19, 2005, p. A1 (reporting that a live grenade thrown at President Bush in 2005, had it detonated, could have injured him from 100 feet away).
The protesters suggest that the agents could have moved the President’s supporters further to the west so that they would not be in range of the President when the motorcade drove from the Inn to the cottage where the President would stay overnight. As earlier explained, however, there would have been no security rationale for such a move. In contrast to the open alley and parking lot on the east side of the Inn, to the west of the Inn where the supporters stood, a large, two-story building blocked sight of, or weapons access to, the patio the agents endeavored to secure. No clearly established law, we agree, required the Secret Service “to interfere with even more speech than security concerns would require in an attempt to keep opposing groups at roughly equal distances from the President.”And surely no such law required the agents to attempt to maintain equal distances by “prevail[ing] upon the President not to dine at the Inn.”

As I read the opinion, the Court is saying that the Secret Service was treating the anti-Bush demonstrators differently based on their physical position, and the potential “unobstructed view” and therefore unobstructed line of attack that it offered against the President, rather than treating them differently based on their viewpoints. The action might have a disparate impact on the groups based on their viewpoint, but such disparate impact, in the absence of discriminatory intent, generally doesn’t suffice to make a government action viewpoint-based (see, e.g., cases such as Frisby v. Schultz, the residential picketing case). I don’t think that, in context, the “But safeguarding the President is also of overwhelming importance in our constitutional system” language suggests that the Court saw this as viewpoint discrimination, but treated it as justifiable viewpoint discrimination.