Trafalgar Law, a prominent character from the manga and anime series One Piece, was indeed once one of the Seven Warlords of the Sea. This title, bestowed by the World Government, grants individuals significant authority and influence in exchange for assisting in maintaining global order. The acceptance of the Warlord title provided Law and his crew with a degree of protection from the Marines while allowing them to pursue their own agendas.
The Warlord system itself was created to balance the power of the Three Great Powers: the Marines, the Emperors (powerful pirate captains), and the Warlords themselves. By aligning with powerful pirates, the World Government aimed to control the seas and prevent any single faction from dominating. Benefits of the position included pardons for past crimes, freedom from direct government intervention, and the ability to operate with a certain level of impunity.