Chief Justice John G. Roberts Jr. is rarely on the losing side of Supreme Court decisions. He is even less frequently on the losing side of high-profile rulings. And he is hardly ever in dissent in cases in which he stands alone with the court’s three liberal justices.

But that is where the chief justice found himself on Monday, when the Supreme Court’s five other Republican nominees voted to allow President Trump’s lavish White House ballroom project to move ahead, likely putting it back on track to completion, despite questions about the legality of the construction.

The case showed the limits of the chief justice’s ability to assemble a majority on the bench he has led for more than two decades, and the limits of the court’s capacity to restrain the president’s boundary-pushing approach to governing.

The court’s other five conservatives concluded that the group that sued did not have legal standing to do so. They did not address the legality of the project, which is estimated to cost $400 million.

As a history buff, Chief Justice Roberts infused his dissent with the words of Winston Churchill and Theodore Roosevelt, showing his appreciation for preservation. In his understated way, he suggested that he was distressed by what the president was doing to the White House without seeking congressional approval.

The mere millions Congress allocated for “ordinary Executive Residence maintenance,” such as refurnishing, air conditioning and lighting, the chief justice wrote, “likely does not authorize the president to use hundreds of millions of dollars in private donations to tear down the East Wing and construct a ballroom in its stead.”

The construction, he concluded bluntly, was “likely unlawful.”

Richard Lazarus, a law professor at Harvard, said it was a significant statement for the chief justice to assign himself the dissent and to write at length in a case that came to the court on its quick-turn emergency docket.

“He writes expansively and treats it with a level of significance, and he’s quite passionate,” said Professor Lazarus, a close observer of the Roberts-led court. Instead of writing a technical, brief rebuttal, the chief justice “suggests this kind of assertion of presidential authority was particularly objectionable,” Professor Lazarus added.

Chief Justice Roberts and his colleagues have insisted the justices should not be seen as political actors, as polls indicate that public trust in the court has declined. To that end, Professor Lazarus said the dissent showed clearly that Chief Justice Roberts believed Mr. Trump’s passion for the ballroom project should “play no role” in how the court decided the case.

In the Supreme Court term that ended on the last day of June, the chief justice demonstrated firm control, assigning himself the task of writing the most significant opinions. He was in the majority in 96 percent of argued cases, more than any other justice.

He wrote the court’s decision invalidating Mr. Trump’s use of emergency powers to impose sweeping tariffs. Another Roberts ruling blocked the president’s plan to limit the longstanding guarantee of citizenship for babies born in the United States; a third prevented Mr. Trump from immediately removing a member of the Federal Reserve Board of Governors.

In all three, the chief justice assembled coalitions that included the three liberal justices and at least one of Mr. Trump’s three nominees — Justices Neil M. Gorsuch, Brett M. Kavanaugh and Amy Coney Barrett.

But he did not when it came to the president’s ballroom project.

The chief justice oversees emergency requests from the U.S. Court of Appeals for the District of Columbia Circuit, where the challenge to the 90,000-square-foot ballroom originated. In their lawsuit, preservationists asserted that the Constitution and federal statutes gave Congress control over federal property, including the “People’s House,” as the White House is often called.

As a result, the chief justice would have had the first crack at proposing to his colleagues how the president’s emergency request to approve the construction should be resolved.

But while Justices Sonia Sotomayor, Elena Kagan and Ketanji Brown Jackson apparently sided with his proposal, the chief justice was unable to find a critical fifth vote.

It was an unusual spot for the chief justice, who writes dissenting opinions infrequently. Since 2020, he has on average voted with the majority in argued cases that were not unanimous 91 percent of the time. Throughout his tenure, he has voted with the majority 83 percent of the time — the fifth highest of any justice and the highest of any chief justice since 1953, according to an analysis by Lee Epstein, a political scientist and law professor at Washington University in St. Louis.

The chief justice’s dissent was surprising for another reason. Even before President George W. Bush nominated him to join the bench in 2005, he had a reputation as a hawk when it came to the court’s gate-keeping role of deciding the procedural — but important — question of who gets to sue.

The majority concluded that the historic preservationists challenging the ballroom construction did not meet the legal mark known as standing, finding that “mere offense, disagreement or distaste does not qualify.” In an unsigned order, the majority said that such a limitless view of who can sue would “seemingly usher in a world where ‘virtually every citizen had standing to challenge virtually every government action that they did not like.’”

The chief justice found otherwise. He said that an architectural historian and longtime member of the National Trust for Historic Preservation, who regularly visits the White House, was sufficiently injured for aesthetic reasons. He credited the historian’s assertion that the new ballroom would “detract from the building’s message of republican simplicity and thereby worsen her viewing experience.”

The conclusion was striking to scholars and lawyers familiar with the chief justice’s past writings that advocated a narrow view of standing.

As a young lawyer in the Reagan administration, Chief Justice Roberts successfully argued in 1990 that an environmental organization did not have legal grounds to sue the Bureau of Land Management.

He doubled down as a lawyer in private practice, writing an influential law review article in 1993 that endorsed tougher limits on standing, insisting that tougher rules would equally affect litigants from across the political spectrum.

“It restricts the right of conservative public interest groups to challenge liberal agency action or inaction,” he wrote, “just as it restricts the right of liberal public interest groups to challenge conservative agency action or inaction.”

Jonathan Adler, a law professor at William & Mary, said conservatives had long wanted to tighten the requirements for standing to prevent courts from substituting their views for the president’s. The chief justice, Professor Adler said, had long been sympathetic to those concerns.

The disagreement over the ballroom came down to differing views on how to apply a landmark 1992 decision on the subject, written by Justice Antonin Scalia, and subsequent Supreme Court rulings involving environmentalists. In Lujan v. Defenders of Wildlife, the court curtailed the ability of environmental groups to challenge government policies, even as it affirmed that conservationists who wanted to observe a particular endangered animal species could have a legally recognized stake to sue “even for purely esthetic purposes.”

In his dissent, the chief justice emphasized that there was no real difference between the environmentalists and an architectural historian who wanted to look at a historic building or object.

But the majority said that type of aesthetic harm was not sufficient to clear the bar, and that litigants had to show “more than mere offense,” disagreement or distaste.

Justice Kavanaugh, one of the majority votes in Monday’s ballroom decision, has written several opinions focused on standing, including the court’s 2024 decision ensuring access to abortion medication. The anti-abortion doctors and medical associations who challenged the F.D.A.’s regulations, he wrote, could not show they were directly harmed and therefore did not have legal grounds to sue.

As with the ballroom perhaps, some legal questions do not get answered in court.

“Some issues,” he wrote at the time, “may be left to the political and democratic processes.”