It may be logical, but I don't believe there is any legal requirement. So my question still remains open.
Here's the list if anyone's interested in searching. I recommend the biographies, not the backgrounds. http://www.oyez.org/oyez/portlet/justices/ Just picking a few at random, I come across Henry Baldwin, who was, indeed, a lawyer. But how's this for a Supreme Court Justice? Did you know that President George Washington's nephew, Bushrod (seriously!), a "short, untidy man," whose tenure is considered "average to forgettable," also served our nation's highest court?
Weird. On that oyuz link, when you click on the name of a justice and it takes you to their page, on the links grouping to the left, where you choose from the links 'background', 'bio', etc., one of the links is 'baseball', and it gives you a multiple choice question such as, Chief Justice John Marshall is most like player A, B, C, or D. It did that on each of the various justices I clicked on. Is there a connection to that site and baseball? Or is there some natural connection between the sport and the Supreme Court that I've overlooked?
when you make a comment like that, you either explain or will be casted off as a loud anitamerican hothead.