In an apparent opening salvo in the looming battle between Republicans in Congress and President Obama, a lawyer for the House of Representatives filed a lawsuit on Friday claiming the Obama administration acted illegally and unconstitutionally by unilaterally amending the president’s health care reform law.

The House voted in July to authorize the lawsuit against the administration, but the actual filing of the litigation comes a day after Obama announced that he would use his executive authority to unilaterally shield from deportation up to 5 million illegal immigrants in the US. He took the action despite furious opposition from Republicans in Congress.

It is unclear whether the timing of the ACA lawsuit was linked to Obama’s immigration announcement Thursday night.

The lawsuit accuses the administration of bypassing Congress to:

Potentially divert $178 billion over 10 years to fund a key aspect of the Affordable Care Act.

Unilaterally amend the ACA by postponing the effective date of the employer mandate – and its penalties – for a year from January 2014 to January 2015.

Enact a regulation to change the terms of the employer mandate.

As passed by Congress, the mandate required large companies to provide government-approved health insurance to all of their employees or face a tax penalty. That requirement was changed by a Treasury Department regulation that declared that employers would not face ACA tax penalties as long as they offered approved health care coverage to 70 percent of their full time employees in 2015 and to 95 percent in 2016.

Those provisions do not appear in the legislation passed by Congress.

In a 28-page complaint filed in federal court in Washington, lawyers for the House charge that the Obama administration usurped powers that the Constitution reserves exclusively to the legislative branch of government.

“The Administration has made no secret of its willingness … to act without Congress when Congress declines to enact laws that the Administration desires,” the complaint says.

“Not only is there no license for the Administration to ‘go it alone’ in our system, but such unilateral action is directly barred by Article I [of the Constitution],” the suit says. “Despite such fundamental constitutional limitations, the Administration repeatedly has abused its power by using executive action as a substitute for legislation.”

The complaint was filed by Jonathan Turley, a constitutional law professor at George Washington University Law School, who was hired by the House Republican leadership to sue the administration.

Mr. Turley is a long-time critic of expansive claims to power by the executive branch.

In its suit, the House is asking US District Judge Rosemary Collyer to declare the administration’s actions illegal and unconstitutional and to block the Treasury Department from making any further diversion of payments.

The suit names Treasury Secretary Jacob Lew and Health and Human Services Secretary Sylvia Burwell as defendants, as well as their agencies.

“Time and time again, the president has chosen to ignore the will of the American people and re-write federal laws on his own without a vote from Congress,” House Speaker John Boehner (R) of Ohio said in a statement.

“If this president can get away with making his own laws, future presidents will have the ability to as well,” he said. “The House has an obligation to stand up for the Constitution.”

House minority leader Nancy Pelosi (D) of California said the case was “meritless.”

“This lawsuit is a bald-faced attempt to achieve what Republicans have been unable to achieve through the political process,” she told the Associated Press. “The legislative branch cannot sue simply because they disagree with the way a law passed by a different Congress has been implemented.”

In its lawsuit, the House highlights what it says is a diversion of funding from one section of the ACA to another that was never authorized by Congress. The unfunded section of the law relates to billion-dollar payments that were to be made to insurance companies.

According to the suit, that section of the law was to be funded through annual appropriations approved by Congress. But, the suit says, Congress has never authorized such payments.

Rather than seeking authorization or an amendment from Congress, administration officials allegedly engaged in creative bookkeeping and sought to fund the insurance payments through an Internal Revenue Service account that did not require an annual approved appropriation from Congress.

“The Constitution does not permit such a sleight of hand,” the lawsuit says. “Absent enactment of a law appropriating funds for [the insurance company program] – and no such law exists – defendants may not legally or constitutionally make [insurance company program] payments to insurers.”

The lawsuit says that so far $3.978 billion has been paid through that program to insurance companies.

The case is United States House of Representatives v. Burwell (14cv1967).