NASHVILLE, Tenn. (AP) — Former Republican presidential candidate Fred Thompson is registering as a lobbyist for a Tennessee trial lawyers group.The Tennessee Association for Justice announced Tuesday that the former U.S. senator would be joining its legislative team this session.Thompson was a lawyer and an actor before being elected to the U.S. Senate in 1993, only to turn his back on politics after his first full term in favor of a full-time acting career in 2002.He was best known for his role as the gruff district attorney on NBC's "Law & Order" before leaving the show in 2007 to run for president.