The Federal Government has started using 18 U.S.C. sec. 1519 to charge "anticipatory obstuction of justice." T. Markus Funk wrote an excellent artice in the May 2011 edition of the "Champion." In a "normal" obstruction of justice case the government must prove four things: (1) the defendant knowingly engaged in an obstructive act; (2) the act impacted an issue or matter with in the jurisdiction of ANY U.S. department or agency; (3) defendant acted at least in relation to or in contemplation of suck prospective issue; and (4) WHICH specific pending proceedings. Now section 1519 does not require the state to prove element four. This leads the state with wide and unfettered ability to charge anticipatory obstruction of justice. So basically if you destory anything after some letter form the government arrives you could be facing federal prosecution.