In a lawful manner; in accordance with law; without violating law; legally: as, we may lawfully do what the laws do not forbid.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
ad. in a manner acceptable to common custom
ad. by law; conforming to the law
Word Usage
"There he would show some old letters of marque, swear that he was a privateer, and had captured the goods lawfully from the enemy, for the world was always at war in those days."