Almost exactly a century ago, in February 1925, Chief Justice William Howard Taft persuaded Congress to grant the Supreme Court an extraordinary power: to pick which cases it would decide.

Most courts do not get to choose the cases they will hear, and their central task is to resolve disputes one at a time. The Supreme Court, by contrast and by dint of the largely unfettered discretion over its docket granted by the Judiciary Act of 1925, understands its job to be quite different: to announce legal principles that will apply in countless cases.

The law effectively changed the court into a policymaking body, and the nation has yet to come to terms with “the immense powers of this new role,” Robert C. Post, a professor at Yale Law School and its former dean, wrote in a new study.

“The transformation has led to an ever-deepening crisis of the court’s authority,” he added.

Justice Neil M. Gorsuch made the key distinction — between resolving individual disputes and setting down broad legal principles — when the court heard arguments in April on Donald J. Trump’s claim, as a former president, of absolute immunity from prosecution.

“I’m not concerned about this case,” Justice Gorsuch said, adding, “We’re writing a rule for the ages.”

Granting the court the power to set its own agenda has caused it to gravitate toward particular sorts of cases, Karen M. Tani, a law professor at the University of Pennsylvania, argued recently in the annual foreword to The Harvard Law Review.