The Keystone XL pipeline may be dead, but the litigation over it lives on.

On Tuesday, attorneys general from six states along the proposed pipeline trail and lawyers from the U.S. Chamber of Commerce and National Association of Manufacturers filed amicus briefs in energy giant TransCanada’s lawsuit against four Obama Cabinet members saying that the president had exceeded his authority in rejecting the project.

In a reprise of arguments used in immigration disputes and other cases involving President Obama’s executive authority, the attorneys general and the Chamber argue that Obama trampled on the power of Congress and the states to regulate interstate and international commerce.

The Chamber and manufacturing trade group also claim that the rejection of the Keystone XL pipeline permit – about seven years after the first application was made – has caused harm by costing states jobs, tax revenue and “billions of dollars of economic activity.” The pipeline would have carried thick crude from Canada’s oil sands to modern refineries on the Texas Gulf Coast. It would have created a couple of thousand jobs while under construction but only about 50 once in operation.

The administration on April 1 moved to have the case dismissed, and the federal court in the southern district of Texas is considering the motion – but the case isn’t clear cut.

The government argues that Obama, by saying the pipeline conflicted with the national interest, treated the project as part of his power to make foreign policy. He said that approving the pipeline would hurt his efforts to persuade other countries to take “ambitious action to combat an urgent global environmental threat.”

The administration also says that for nearly 150 years, the president’s authority to make this sort of decision had gone unchallenged. President Grant imposed conditions on a private company seeking to lay a telegraph cable from France. President Kennedy approved an oil pipeline between the United States and Canada. President George W. Bush’s 2004 executive order set rules to speed administration approvals of pipelines.

Indeed, the government said, even Congress in December 2011 had acknowledged Obama’s power when it sent him legislation that sought to force his hand and require him to approve the Keystone XL. Seeking to help TransCanada, the Congress sought to require Obama to “grant a permit under Executive Order No. 13337” – the order issued by Bush in 2004.

Constitutional lawyers say that in general, presidential authority not clearly set out in the Constitution could fall into one of three boxes, originally described in a concurring opinion by Justice Robert Jackson in a 1952 case that limited President Truman’s power to seize steel mills during wartime to head off a strike by workers.

The first box is the clearest: Congress clearly delegates authority through legislation. The third box in the murkiest: The president acts in a way inconsistent with the expressly stated will of Congress.

The Obama administration is seeking refuge in the middle, in the second box: There the president acts independently in an area where Congress has not acted to limit his authority.

“In the nearly one and a half centuries of executive exercise of authority over a wide range of cross-border facilities, Congress has never questioned the president’s authority,” the government said in its 57-page brief. “Instead, it has either explicitly affirmed the executive’s authority over specific types of border-crossing facilities or has remained silent and thereby accepted the president’s authority.”

TransCanada is seeking billions of damages in the case. Its priority is commercial, not political. It names as defendants Secretary of State John F. Kerry, Attorney General Loretta E. Lynch, Interior Secretary Sally Jewell and Homeland Security Secretary Jeh Johnson.

But the amicus briefs, like those in other politically charged cases, took aim at Obama’s exercise of executive authority at a time of congressional paralysis.

The Chamber’s lawyers, led by Theodore J. Boutrous Jr. of Gibson Dunn & Crutcher, condemned Obama’s “remarkable assertion” that rejecting the pipeline would be “a useful bargaining chip” in negotiations with foreign nations. He said that Congress “never acquiesced” to the “novel assertion of presidential power.”

The state attorneys general said that the national interest argument about preserving credible American leadership on climate issues was weak. “If such tenuous connections to international stature and potential foreign negotiations is sufficient to provide the President constitutional authority to act, there is virtually no limit to the power of an enterprising President to dream up reasons to exercise authority far beyond what the Constitution contemplates in a manner that could prove disastrous to the States,” their brief said.

One irony of the state attorneys general brief: It was filed on behalf of Montana, South Dakota, Nebraska, Kansas, Oklahoma and Texas. But Oklahoma and Texas already have their segments of the pipeline. Obama approved the southern leg of the original Keystone XL proposal, so that the line is currently operating from Cushing, Okla. to Port Arthur, Texas.

No matter. If the pipeline can’t supply crude oil from Canada, it can supply fodder for the battle over Obama’s executive authority.