A lawsuit challenging Pennsylvania's mandatory retirement age of 70 for judges was dismissed Tuesday by a federal judge who wrote that only voters have the power to change the 1968 amendment to the state constitution.

U.S. District Judge John E. Jones III of Harrisburg wrote: "There is at least a superficial irony in having a [federal] judge who is appointed for life . . . rule against his judicial colleagues on the courts of this commonwealth who must hang up their robes at age 70. And we confess that this causes us no small amount of discomfort.

"But at the end of the day," Jones continued, "it is for the citizens of the commonwealth and their elected representatives to amend and alter the subject provision, not this court."

Jones noted that the state Senate Judiciary Committee is considering legislation that would raise the retirement age for state court judges to 75.

Representatives of the judges who filed the suit, challenging the Pennsylvania retirement rule under equal protection and age-discrimination theories, were not immediately available for comment.

In the interim, the judges could appeal Jones' decision to the U.S. Court of Appeals for the Third Circuit. But Jones' opinion made clear that the outcome of such an appeal is far from certain. In 1980, the Third Circuit rejected a similar lawsuit by Pennsylvania state judges, a ruling that the U.S. Supreme Court declined to review. Then, in 1991, the U.S. Supreme Court upheld a Missouri constitutional provision requiring that state's judges to retire at 70.

This year, a similar effort by Pennsylvania judges was rejected by the state Supreme Court, which also ruled that only the legislature and the voters can amend the state constitution.

The dozen state judges challenging the Pennsylvania retirement provision include Philadelphia Common Pleas Court Judge Benjamin Lerner, who continues to oversee the pretrial proceedings in every Philadelphia homicide case although he turned 70 in 2011.

Like many other so-called senior judges, Lerner continues serving on a per-diem basis for up to 10 days a month, though he concedes that he is often on the bench twice that amount of time.

Pennsylvania is among 30 states with a mandatory retirement age for judges, and some jurists who have reached that milestone argue that the rationale behind the retirement rule - increasing incidence of infirmity and senility - has been outstripped by modern medicine.

Contact Joseph A. Slobodzian at 215-854-2985, jslobodzian@phillynews.com or on Twitter @joeslobo