A federal appeals court in Washington upheld the Obama administration’s health care law on Tuesday in a decision written by a prominent conservative jurist.

The decision came as the Supreme Court is about to consider whether to take up challenges to the Affordable Care Act, a milestone legislative initiative of the administration.

Of four appellate court rulings on the health care law so far, this is the third to deal with the law on the merits, and the second that upholds it.

The United States Court of Appeals for the District of Columbia Circuit in Washington issued the 37-page opinion by Judge Laurence H. Silberman. In the opinion, Judge Silberman, who was appointed by President Ronald Reagan, described the law as part of the fundamental tension between individual liberty and legislative power.

“The right to be free from federal regulation is not absolute, and yields to the imperative that Congress be free to forge national solutions to national problems, no matter how local — or seemingly passive — their individual origins,” he wrote. The fact that Congress may have never issued an individual mandate to purchase something before, a central argument for many opposing the law, “seems to us a political judgment rather than a recognition of constitutional limitations,” he wrote.

A 65-page dissent by Judge Brett M. Kavanaugh, a conservative jurist appointed by President George W. Bush, stated that the courts lack jurisdiction until the law’s tax penalties take effect in 2015. Citing the 19th-century Anti-Injunction Act, he said that the “important and long-standing” law “poses a jurisdictional bar to our deciding this case at this time.”

The split among the appellate courts increases chances that the Supreme Court will hear the case. Tuesday’s opinion is the second appeals court decision that upholds the law on the merits. The Court of Appeals for the 11th Circuit, based in Atlanta, struck down the individual mandate in a suit brought by officials of 26 states, and experts say it is most likely to be among those that the Supreme Court will choose to hear if the judges decide to take up the cases at their private conference on Thursday.

The White House posted a blog entry by Stephanie Cutter, a senior aide to the president, that hailed “yet another victory” for Americans getting benefits from the early elements of the bill.

The fact that two leading lights of conservative jurisprudence decided against positions held by opponents of the health care law threatens to upend the popular notion that the fate of the law will be determined by judges along political lines. In lower courts, judges appointed by Republican presidents did tend to rule against the law while those appointed by Democrats issued rulings in its favor. Those expecting the pattern to continue have predicted defeat for the law at the Supreme Court.

Jack M. Balkin, a constitutional scholar at Yale Law School, said that what is emerging at the appeals level, including a June decision supporting the law from the Sixth Circuit that with a concurrence by Judge Jeffrey S. Sutton, another Bush appointee, shows “it’s actually a much more complicated story about how judges are seeing this act.”

In fact, Professor Balkin said, conservative legal theory runs deeper than politics, with two schools of thought. The one that emerged in Tuesday’s decision “emphasizes judicial restraint and respect of political branches when they attempt to make national economic policy.” The other school, he suggested, “argues for robust judicial review to protect constitutional values that conservatives hold dear, for example, federalism and individual liberty.”

Elizabeth B. Wydra, chief counsel to the Constitutional Accountability Center, a Washington group that supports the law, underscored that point in a statement that called the decision “a devastating blow to the challengers of the act, delivered by one of the country’s foremost conservative jurists.”

A conservative legal organization that took part in the suit opposing the law, the American Center for Law and Justice, expressed disappointment. Jay Sekulow, the chief counsel for the group, said “we still remain confident that ObamaCare and the individual mandate, which forces Americans to purchase health insurance, is the wrong prescription for America and ultimately will be struck down as unconstitutional by the U.S. Supreme Court.”

Randy E. Barnett, a professor at Georgetown University’s law school and an opponent of the law, said: Judge Silberman’s opinion “rests on his claim that Congress has an unlimited power to address whatever it deems to be a national problem. Fortunately, his will not be the last word on these constitutional challenges.”