For a fleeting moment this fall, U.S. District Judge Robert N. Scola Jr. declared in jest that he wished he were “king of the world.”

If he had such power, Scola said from the bench, he would deny a defense lawyer’s request to travel to Pakistan to question a group of defendants charged in a Miami terrorism case along with two Muslim clerics. Since the missing defendants weren’t present, the judge considered them “fugitives.’’

But the judge let the defense team make the upcoming trip against fierce opposition from prosecutors, because case law allows such extraordinary depositions, he found.

Scola, a former Miami-Dade prosecutor and state circuit court judge, relishes his role as one of three new members on South Florida’s federal bench, which is experiencing a generational sea change as the result of several retirements and presidential appointments.

“I knew I wanted to be a judge when I was 10 years old; my father was a judge in Massachusetts,” Scola said, during a brief December interview wedged between verdicts in the South Beach “bar-girls” trial and the sentencing of a mental-health clinic director convicted of Medicare fraud.

Over the past few years, the federal court in the Southern District of Florida has seen the departure of four judges — Daniel T.K. Hurley, Paul C. Huck, Alan S. Gold and Patricia A. Seitz — who have gone on “senior” status, meaning they handle lighter caseloads. Another federal judge, Adalberto Jordan, was confirmed this year as a member of the 11th U.S. Circuit Court of Appeals in Atlanta.

Those five vacancies, in one of the busiest federal districts for criminal and civil cases in the country, accounted for about one-third of all the positions on the federal bench in South Florida.

The retirements have generated coveted openings that have been filled by Scola, 57; Kathleen M. Williams, 56, a former Miami federal public defender; and Robin S. Rosenbaum, 46, a former Fort Lauderdale federal magistrate judge. Rosenbaum, also a one-time federal prosecutor, was sworn in as a new U.S. district judge Dec. 13.

“It’s pretty obvious that Robin is never going to make a decent living,” 11th Circuit Judge Stanley Marcus, for whom Rosenbaum once clerked, quipped about her public-service career during her investiture in Fort Lauderdale federal court.

But then Marcus struck a more serious note, describing federal district judges as the “crucible of justice” in the U.S. court system. “I have to say, Robin, this is work you were born to do,” he said.

Another recent nominee: Miami-Dade Circuit Judge William L. Thomas, a former assistant public defender in both the state and federal system. Thomas is scheduled for confirmation as a federal judge in 2013. If confirmed, he would become the first openly gay black man appointed to a federal judgeship in the nation.

Michael Caruso, the Miami federal public defender who replaced Williams in August, said the appointment of federal judges is in many ways a “president’s most enduring legacy.”

“All presidents strive to appoint smart, fair and hardworking lawyers,” Caruso said, commenting on the four nominated by President Barack Obama in South Florida. “President Obama, in addition to choosing women and men who share these traits, has chosen those who’ve been trial lawyers in the criminal justice system and who have devoted a significant portion of their career to public service.”