After Rep. David Graves was charged with drunken driving for a second time, he and his lawyer offered a surprising defense: As a lawmaker, Graves cannot break the law — at least not while the Legislature is at work. The Macon Republican is using an obscure provision in the state constitution to argue that he should not be prosecuted for a DUI he received in Cobb County in February, during the 2005 session of the General Assembly. The centuries-old provision holds that a lawmaker cannot be arrested during sessions of the General Assembly, legislative committee meetings or while they're "in...