As Justice John Paul Stevens is so ably about to prove, “90″ may be the new “70,” at least for judges, and state lawmakers are taking note.

Stevens announced last week that he would retire when the current Supreme Court term ends. He will turn 90 on April 20. If Stevens were a state Supreme Court justice, he would not have had the option of choosing when to retire because most states require those judges to step down after age 70, according to the National Center for State Courts in a recent study. But nine states this year have legislation pending that would either eliminate or raise the retirement age.

The Center noted that 20 states require retirement at age 70; four at 72; two at 74, and six at 75. Vermont is the only state with a mandatory retirement age of 90 for a state Supreme Court justice.

If applied to the U.S. Supreme Court, those states’ retirement rules would force from the bench not only Justice Stevens, but also Justices Antonin Scalia, Anthony Kennedy, Ruth Bader Ginsburg and Stephen Breyer.

In 2009, the Center reported, Kansas increased the age at which their justices must retire from 70 to 75, and South Dakota’s House of Representatives also approved an increase from 70 to 75.

The nine states that have recently considered or are considering legislation to increase or eliminate mandatory retirement ages for state judges are: Alabama (from 70 to 72); Arizona (70 to 75); Massachusetts (70 to 76); New Hampshire (70 to none); New Jersey (70 to 75); New York (70 to none); Virginia (70 to 73); Washington (75 to none) and Wyoming (70 to none).

Justice Stevens’ career, of course, is not the trigger for the action in the state legislatures. William Raftery, a court research analyst at the Center first noted what could be an emerging trend back in February.

Raftery suggested that the states have begun to reexamine mandatory retirement rules as the Baby Boom generation ages, life expectancies increase, and more veteran and able judges are forced into retirement.

The Center provided a chart showing how many states would allow the current members of the U.S. Supreme Court to remain on the bench:

Justice Date of birth Current age No. of states & D.C.
where he/she would
still be on the bench
John G. Roberts 1/27/55 55 51
John Paul Stevens 4/20/20 89 19
Antonin Scalia 3/11/36 74 25
Anthony Kennedy 7/23/36 73 27
Clarence Thomas 6/23/48 61 51
Ruth Bader Ginsburg 3/15/33 77 19
Stephen Breyer 8/15/38 71 31
Samuel Alito 4/1/50 60 51
Sonia Sotomayor 6/25/54 55 51

Source: U.S. Supreme Court, Biographies of Current Justices of the Supreme Court