WordNet sense 1 (logically valid):

sound, well-grounded

WordNet sense 2 (based on known statements or events or conditions):

legitimate, logical, legitimate

WordNet sense 3 (having legal efficacy or force):

effectual, legal

WordNet sense 4 (executed with proper legal authority):

binding

WordNet sense 5 (not having come to an end or been terminated by passage of time):

unexpired