John G. Roberts Jr. is breathing the kind of air that the rest of us can only dream about, the air of kings and queens and one-name celebrities like Oprah.

He's got Mick Jagger juice now, baby.

They're the folks who possess that rarest of powers -- they've got a job for life. Roberts is right up there with the pope in terms of job security. That is, as long as he lives up to the Constitution's demand of "good behavior."

After being sworn in yesterday afternoon as the nation's 17th chief justice, Roberts said he planned to show up at the office today. But if he doesn't, there's not a thing anybody can do about it. The media might fuss and others might grumble, but that would be it. It would take an act of Congress to fire the guy.

If he wants to take a break every Thursday morning to play tennis -- as his mentor and predecessor, the late William Rehnquist, did -- no problem. The only clock he's got to punch for the rest of his life is his own. And, as so many senators liked to point out during the recent confirmation hearings, Roberts is just 50, the youngest chief justice in two centuries. If he does play tennis weekly -- or golf, or whatever -- and eats well, there's a good chance that Roberts will outlast at least four presidents.

Mark Tushnet is in the same orbit -- kinda. He's a tenured law professor at Georgetown and life, he'll gladly tell you, isn't bad. He's been tenured since about 1977. "It's been so long, I can't remember exactly," he says. He likes the fact that just the other day he could leave the office early to see his new grandchild. And it's a nice life when you can take the afternoon off and go to a baseball game and no one asks any questions. Not that he would do that, of course.

(And his colleagues at the American Association of University Professors will gladly point out that although tenure may look like a lifetime appointment, there are ways that you could end up out of a job.)

Still, the Supreme Court is another kind of universe. "If there were an ad for the job, it would be, 'Inside work, no heavy lifting,' " Tushnet says. "The justices hear only the cases they want to hear, write only what they want to write. It's great."

Don't misunderstand, though. Being on the Supreme Court is not like taking a lifelong stroll across the Mall. "These people take their jobs seriously. They don't slack off as some people say tenured professors do," Tushnet says and chuckles.

"There was this joke from the 1960s," he says. "There was a period when Justice [Potter] Stewart and Justice [Thurgood] Marshall saw each other only when Justice Marshall was leaving the office at 2 and Stewart was arriving at 2. . . . But everybody agreed they did the work."

There's something quite lovely and possibly life-extending about being able to control your own time.

Sara Rix, a policy adviser for AARP, doesn't know the precise health benefits of lifetime job security, but she said she has read studies that show that "people who remain in the labor force late in life tended to be healthier, better educated and more affluent than others not in the labor force."

And these days, Roberts will be in step with his generation. "Over a third of boomers expect never to retire," Rix says.

Monsignor Brian Ferme is dean of canon law at Catholic University. Talking to him is like chatting with actor Michael Caine. He even looks like the guy and says he "has been accosted on the street for an autograph."

"But I'm younger -- in my fifties -- and fatter," he jokes.

But we digress.

There are some similarities, he supposes, between his calling to the priesthood and folks serving a lifetime appointment as a federal judge. At least when it comes to job security.

But, he adds, "he can retire . . . whereas you can't retire from ever being a priest."

The pope can retire, too, he says, though that hasn't happened for centuries.

John Roberts takes the oath as the nation's 17th chief justice, and it's a job supreme -- good for life.

Lifers all: Pope Benedict XVI in Saint Peter's Square; John Roberts is congratulated by Justice John Paul Stevens, below left, along with President Bush and Roberts's wife, Jane; and tenured college professor Mark Tushnet, below right.

Benedict XVI, here acknowledging the faithful during his weekly general audience in Saint Peter's Square, does have the option of retiring -- as pope.