The SB1070 fiasco is virtual proof why border and internal immigration law enforcement is NOT possible as part of so called Comprehensive Immigration Reform.
...What advocates call 'comprehensive immigration reform' is sold as a package, a grand bargain, of amnesty for illegal aliens (and increased legal immigration) in exchange for tougher enforcement in the future. But if the Arizona experience has taught us anything, it's that any new enforcement measure will be tied up in the courts for years. This makes a grand bargain impossible, almost by definition: The amnesty part of the deal would be implemented immediately, while the promised enforcement would languish in court and might never survive...
From the Center of Immigration Studies.