President violates oath and doesn't enforce the law, that is OK; State tries to help enforce federal law (which the Federal government doesn't have to deport or punish illegals), not OK

Charles Krauthammer as a useful piece in the Washington Post:

And there’s the rub: the Obama administration’s inability to distinguish policy from law. This becomes particularly perverse regarding immigration when, as Justice Antonin Scalia points out, what the administration delicately calls its priorities is quite simply a determination not to enforce the law as passed.
This is what makes so egregious the Obama claim that Arizona is impermissibly undermining federal law. “To say, as the court does,” writes Scalia regarding those parts of the law struck down by the majority, “that Arizona contradicts federal law by enforcing applications of the Immigration Act that the president declines to enforce boggles the mind.”
Consider this breathtaking cascade: An administration violates its constitutional duty to execute the law by deliberately refusing to enforce it. It then characterizes its non-enforcement as simply establishing priorities. It then tries to strike down a state law on immigration on the grounds that it contradicts federal law — by actually trying to enforce it! . . . 

The same is true with other issues.

Obama’s presumption is Olympian. He takes America into a war in Libya with U.N. approval but none from Congress. Yet that awful Bush had the constitutional decency to twice seek and gain congressional approval before he initiated hostilities. The Department of Health and Human Services issues Obamacare regulations treading so heavily on the free-exercise rights of Catholic institutionsthat Obama’s own allies rebel. The new regulation concocted to tame the firestorm blithely orders private insurers to provide free contraceptives to employees of the objecting religious institutions. By what possible authority does a president order private companies to provide free services? To say nothing of the 1,200 Obamacare waivers granted with royal arbitrariness according to the (political) whims of an HHS secretary. . . .

Strassel has this piece in the WSJ (the whole piece has lots of examples):

Put another way: Mr. Obama proposes, Congress refuses, he does it anyway. 

For example, Congress refused to pass Mr. Obama's Dream Act, which would provide a path to citizenship for some not here legally. So Mr. Obama passed it himself with an executive order that directs officers to no longer deport certain illegal immigrants. This may be good or humane policy, yet there is no reading of "prosecutorial discretion" that allows for blanket immunity for entire classes of offenders. 
Mr. Obama disagrees with federal law, which criminalizes the use of medical marijuana. Congress has not repealed the law. No matter. The president instructs his Justice Department not to prosecute transgressors. He disapproves of the federal Defense of Marriage Act, yet rather than get Congress to repeal it, he stops defending it in court. He dislikes provisions of the federal No Child Left Behind Act, so he asked Congress for fixes. That effort failed, so now his Education Department issues waivers that are patently inconsistent with the statute. 
Similarly, when Mr. Obama wants a new program and Congress won't give it to him, he creates it regardless. Congress, including Democrats, wouldn't pass his cap-and-trade legislation. His Environmental Protection Agency is now instituting it via a broad reading of the Clean Air Act. Congress, again including members of his own party, wouldn't pass his "card-check" legislation eliminating secret ballots in union elections. So he stacked the National Labor Relations Board (NLRB) with appointees who pushed through a "quickie" election law to accomplish much the same. Congress wouldn't pass "net neutrality" Internet regulations, so Mr. Obama's Federal Communications Commission did it unilaterally. 
In January, when the Senate refused to confirm Mr. Obama's new picks for the NLRB, he proclaimed the Senate to be in "recess" and appointed the members anyway, making a mockery of that chamber's advice-and-consent role. In June, he expanded the definition of "executive privilege" to deny House Republicans documents for their probe into the botched Fast and Furious drug-war operation, making a mockery of Congress's oversight responsibilities. . . .