Leave him in prison until he rots; traitors to the country deserve no less. Or, as Ben Domenech puts it:
. . . Pollard handed over to Israel secrets which were traded to, or otherwise obtained by, the Soviet Union. As former FBI and Navy lawyer M.E. Bowman writes at the U.S. Intelligence Studies journal Intelligencer, in a piece anyone advocating for Pollard’s release really ought to read, Pollard leaked “the daily report from the Navy’s Sixth Fleet Ocean Surveillance Information Facility (FOSIF) in Rota, Spain, a top-secret document filed every morning reporting all that had occurred in the Middle East during the previous twenty-four hours, as recorded by the NSA’s most sophisticated monitoring devices.” He also handed over “the TOP SECRET NSA RAISIN manual which lists the physical parameters of every known signal, notes how we collect signals around the world, and lists all the known communications links then used by the Soviet Union.”
No spy who did so much damage to the national security of the United States, and to American interests in general, deserves clemency of any kind.