To call this version of pre-emption "strained" is an understatement. The DOJ has argued, in effect, that the pre-emption doctrine applies to mere public policy preferences as well as to laws and regulations. Of course, Arizona cannot force the feds to take illegal aliens it apprehends, and it doesn't claim to be able to do so. Since Arizona doesn't do anything other than enforce a federal statute it has concurrent jurisdiction to enforce, there is no legal pre-emption issue. In fact, there is no colorable issue to even bring a complaint. This would be summary judgment bait if it weren't such a charged issue. I suspect the DOJ knows this will be tossed as well as most attorneys who have read the complaint and application for injunction. This is political, not legal, and fairly pathetic.