Source : Webster's Revised Unabridged Dictionary (1913)

Legally \Le"gal*ly\, adv.
   In a legal manner.

Source : WordNet®

legally
     adv 1: by law; conforming to the law; "we are lawfully wedded now"
            [syn: {lawfully}, {wrongfully}, {de jure}] [ant: {unlawfully}]
     2: in a legal manner; "he acted legally"