WordNet sense 1 (someone who has committed (or been legally convicted of) a crime):

criminal, crook, felon, malefactor

WordNet sense 2 (declare illegal; outlaw):

criminalise, criminalize, illegalise, illegalize

WordNet sense 3 (contrary to or forbidden by law):

illegitimate, illicit, outlawed

WordNet sense 4 (prohibited by law or by official or accepted rules):

illegal

WordNet sense 5 (disobedient to or defiant of law):

lawless

WordNet sense 6 (contrary to or prohibited by or defiant of law):

unlawful