WordNet sense 1 (according to custom or rule or natural law):

orderly, rule-governed

WordNet sense 2 (in accordance with fixed order or procedure or principle):

regular

WordNet sense 3 (having a legally established claim):

rightful, true

WordNet sense 4 (of marriages and offspring; recognized as lawful):

legitimate, legitimate

WordNet sense 5 (authorized, sanctioned by, or in accordance with law):

licit

WordNet sense 6 (established by or founded upon law or official or accepted rules):

legal