WordNet sense 1 (having legal efficacy or force):

effectual, sound

WordNet sense 2 (well grounded in logic or truth or having legal force):

valid

WordNet sense 3 (authorized, sanctioned by, or in accordance with law):

lawful, legitimate, licit, legitimate

WordNet sense 4 (decreed by or proceeding from a court of justice):

judicial

WordNet sense 5 (qualified for or allowed or worthy of being chosen):

eligible