You have to have the right personality for law...I have a couple of lawyer friends (one in IP, the other in corporate tax).  The money is good but the hours are long.
If you are interested in CS and think you might want to do research but are also interested in public policy... MIT, Berkeley, Stanford, and Carnegie Mellon have fantastic CS graduate programs and excellent public policy programs.
A couple of my friends here at Carnegie-Mellon are getting joint Ph.D.'s is chemical engineering and public policy...they took all the classes for chemE and public policy and then did their qualifier's and thesis proposals on their central reearch topic, which were designed to have some "policy" aspects (i.e. air quality management, process and chemical system safety, etc.).  Then they'll do their thesis defense in both departments as well.  I'm sure MIT, Stanford, Berkeley, and other U's have similiar program combo's in graduate school.
Either way...best of luck to you!