The Collaborative International Dictionary of English v.0.48:
Lawful \Law"ful\, a.
1. Conformable to law; allowed by law; legitimate; competent.
[1913 Webster]
2. Constituted or authorized by law; rightful; as, the lawful
owner of lands.
[1913 Webster]
Lawful age, the age when the law recognizes one's right of
independent action; majority; -- generally the age of
twenty-one years. Also called legal age or age of
majority.
[1913 Webster +PJC]
Note: In some of the States, and for some purposes, a woman
attains lawful age at eighteen. --Abbott.
Syn: Legal; constitutional; allowable; regular; rightful.
Usage: Lawful, Legal. Lawful means conformable to the
principle, spirit, or essence of the law, and is
applicable to moral as well as juridical law. Legal
means conformable to the letter or rules of the law as
it is administered in the courts; conformable to
juridical law. Legal is often used as antithetical to
equitable, but lawful is seldom used in that sense. --
Law"ful*ly, adv. -- Law"ful*ness, n.
[1913 Webster]