From a Dec. 3 press release

AUSTIN – Texas Attorney General Greg Abbott issued the following statement after taking legal action challenging President Barack Obama’s immigration executive action:

“The President’s unilateral executive action tramples the U.S. Constitution’s Take Care Clause and federal law. The Constitution’s Take Care Clause limits the President’s power and ensures that he will faithfully execute Congress’s laws – not rewrite them under the guise of ‘prosecutorial discretion.’ The Department of Homeland Security’s directive was issued without following the Administrative Procedure Act’s rulemaking guidelines and is nothing but an unlawfully adopted legislative rule: an executive decree that requires federal agencies to award legal benefits to individuals whose conduct contradicts the priorities of Congress.

“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. 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.”

From a Dec. 4 request for a preliminary in junction filed in U.S. District Court in Texas:

Plaintiffs are likely to prevail on the merits. First, the President violated his obligation to “take Care that the Laws be faithfully executed.” The Take Care Clause enshrines the ancient principle that the President cannot dispense with laws he dislikes. Here, Defendants have created an enormous program that will guarantee open toleration and legal benefits to millions of undocumented immigrants who meet the President’s chosen eligibility criteria. They did so in contravention of statutory objectives and in the face of congressional opposition. That is a paradigmatic example of impermissible executive lawmaking, as demonstrated by Supreme Court precedent and the analysis of the President’s own lawyers.

Absent a preliminary injunction, Plaintiffs will be irreparably injured. First, the deferred action plan will set off another humanitarian crisis, much like the one caused by the Defendants’ smaller deferred action plan in 2012. Second, it will be virtually impossible to unscramble the egg once Defendants give out lawful-presence documents to millions of people who are not lawfully present in the United States. Plaintiffs are forced to rely on the federal government to faithfully determine an immigrant’s status, and they will be harmed if the Defendants are allowed to flout that responsibility on a massive scale.