The attorneys general from 17 states have filed suit in federal court seeking to block President Obama's plan to legalize 5 million illegal aliens.

Led by the governor-elect of Texas, Greg Abbott, AGs from other states joining are in Alabama, Georgia, Idaho, Indiana, Kansas, Louisiana, Maine, Mississippi, Montana, Nebraska, North Carolina, South Carolina, South Dakota, Utah, West Virginia, and Wisconsin.

Politico:

“The President is abdicating his responsibility to faithfully enforce laws that were duly enacted by Congress and attempting to rewrite immigration laws, which he has no authority to do — something the President himself has previously admitted,” Abbott said in a statement. “President Obama’s actions violate the Take Care Clause of the U.S. Constitution and the Administrative Procedure Act, which were intended to protect against this sort of executive disregard of the separation of powers.”

The White House responded to the suit by saying it is “confident that the President’s executive actions are well within his legal authorities.” Officials pointed to a memo from the Office of Legal Council justifying their move and a letter from 135 immigration law professors backing them up.

“The Supreme Court and Congress have made clear that federal officials can set priorities in enforcing our immigration laws,” said White House spokeswoman Brandi Hoffine.

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White House officials also pointed to the Supreme Court’s 2012 decision in Arizona v. United States, which they say gave the federal government leeway in setting enforcement priorities, such as deciding that removing smugglers and criminals is more important than removing veterans or students.

The battle over Obama’s order is also playing out in Congress, where some conservatives are pushing, so far unsuccessfully, to defund part of the Department of Homeland Security. Separately, the House is likely to vote next week to condemn the move.

This new lawsuit also argues that the DHS directive required public notice and a comment period that didn’t occur.

“The executive action to dispense with federal immigration law will exacerbate the humanitarian crisis along the southern border, which will affect increased state investment in law enforcement, health care and education,” Abbott said in his announcement.

Indiana Gov. Mike Pence, a Republican who may run for president in 2016, announced that he directed his attorney general to join the suit.

“This lawsuit is not about immigration,” Pence said in a statement. “It is about denying states such as ours the opportunity to be represented in policy making through our elected members of Congress.”

The suit is not denying the premise that the president, as chief executive, can set deportation priorities.  Rather, the states are basing their argument on the "Take Care" clause in Article II, Section 3 of the Constitution ("The President] shall take Care that the Laws be faithfully executed....").  Just because the president can set priorities in immigration enforcement doesn't mean he can ignore his responsibility to faithfully execute the law.  It's a subjective argument, but that's why we have federal judges.

The suit was brought in the Southern District of Texas, where most of the judges were appointed by Republicans.  That may or may not be significant, given the constitutional issues involved.  And the suit will no doubt find its way someday to the Supreme Court.

In the meantime, this new avenue of defense against executive overreach could redefine the relationship between Washington and the several states.