An 1807 law banned importation of slaves and 1820 law made it piracy punishable by death. A Navy/Marine squadron, that began with a mission to fight Barbary pirates, also took on the task of capturing slave ships. But often those slavers convicted received light penalties. That is, until election of Lincoln on GOP platform vowing “total and final suppression” of African slave trade as “crime against humanity.”
The image of the African Slave Patrol Commemorative Medal can be found on Charles P. McDowell’s Foxfall Medals web site in the Military Order of Foreign Wars section at
http://foxfall.com/mofw-cm-astp.htm