Aarti Shahani explained yesterday how Washington spawned Arizona’s SB 1070 by deputizing local cops as immigration officers. That fact leaves the Justice Department appearing to split legal hairs when arguing that Arizona’s law unconstitutionally usurps the feds’ power to control the border. Shahani’s analysis of the DOJ suit against SB 1070 is important, but it’s also worth noting that the door for renegade, state-led immigration enforcement opened long ago. So check out Valeria Fernandez’s interactive timeline of Arizona’s long march toward SB 1070 as well.