‘It’s a huge victory for both the AP and the free press,” Axios’s Sara Fischer wrote of the preliminary injunction Judge Trevor McFadden issued Tuesday in Associated Press v. Budowich. But the victory may prove fleeting—Judge McFadden stayed his order until Sunday to allow for an appeal—and there’s less to it than meets the eye.

‘It’s a huge victory for both the AP and the free press,” Axios’s Sara Fischer wrote of the preliminary injunction Judge Trevor McFadden issued Tuesday in Associated Press v. Budowich. But the victory may prove fleeting—Judge McFadden stayed his order until Sunday to allow for an appeal—and there’s less to it than meets the eye.

The defendants are staffers for President Trump who had limited the wire service’s White House access on ideological grounds, most prominently because it declined to adopt Mr. Trump’s new name for the Gulf of Mexico. Judge McFadden held that amounted to “viewpoint discrimination” in violation of the First Amendment. He decreed that “defendants shall immediately rescind the denial of the AP’s access to the Oval Office, Air Force One, and other limited spaces based on the AP’s viewpoint when such spaces are made open to other members of the White House press pool.”

But he made clear this doesn’t mean a return to the status quo ante: “The AP is not necessarily entitled to the ‘first in line every time’ permanent press pool access it enjoyed under the WHCA”—the White House Correspondents Association, whose control over the press pool the White House ended on Feb. 25. The order doesn’t require “the Government to grant the AP permanent access to the Oval Office, the East Room, or any other media event.” Nor does it “bestow special treatment upon the AP.”

So what does it require? “For the Government to put the AP on an equal playing field as similarly situated outlets,” Judge McFadden wrote. “It cannot be treated worse than its peer wire services.”

Could the White House get around the order by adopting a pretext that doesn’t amount to viewpoint discrimination? By adding Reuters and Bloomberg to its blacklist? By dissolving the press pool and recharacterizing all press events as group interviews?

More important, does Judge McFadden want to spend the next 3½ years micromanaging the White House press shop by refereeing endless disputes between Mr. Trump and the AP over the terms of a settlement or a permanent injunction? Surely not. This case is bound for a higher court.

In that regard, the most crucial part of the judge’s order is a footnote at the bottom of the final page: “The Court notes that the President is not a party to this case, and defense has not argued that an injunction would affect his constitutional authority in any way.”

In fact, the defendants’ Feb. 24 brief did make such an argument, albeit subtly. It asserted that “the President has absolute discretion to give interviews to whomever he pleases” and that the “same discretion extends to whom he allows into the Oval Office (his personal workspace), Air Force One (his personal plane), and Mar-a-Lago (his private residence).”

The AP and Judge McFadden both conceded the point about interviews. But the judge deemed the Oval Office a “nonpublic forum” to which a journalist can claim a First Amendment right of access. That finding violates the separation of powers, because the president’s control over his physical office is intrinsic to the authority of his political office. Imagine if the White House attempted to dictate the operations of the House Press Gallery, or if Congress enacted a law purporting to regulate access to judges’ chambers.

Perhaps the Justice Department lawyers arguing the case thought the latter analogy would be obvious to a judge, who is sovereign in his private workspace. On appeal, they should spell out that the president’s independence is as constitutionally important as the judiciary’s.

Mr. Taranto is the Journal’s editorial features editor.