“Each pay period, there will be more legal weapons being brought into play,”’ Tiefer said.

The creative tactics employed by federal agencies to keep some services going could be probed by a future administration.

“This administration is being creative in its ability to break the law and test the boundaries, so there is a possibility that a future administration” could pursue alleged violations, said Sam Berger, a senior adviser at the Center for American Progress, who worked at the Office of Management and Budget under former President Barack Obama. “With this administration and what you see them doing, they are really walking up to and past that line, and so it raises a serious question. I’d think a future DOJ would have to seriously take a look to see if there were criminal violations here.”

It’s not clear who, outside of the Justice Department, can challenge perceived violations. Federal courts may take a skeptical view of the standing of people claiming to be injured by an agency deciding to spend amid the shutdown.

Legal Challenges

“In general, the courts have been fairly hostile to people saying this expenditure of federal funds is illegal,” said David Kopel, an adjunct professor of constitutional law at Denver University and an adjunct scholar at the Cato Institute. “Their answer to that is ‘maybe it is, but how are you in particular impacted by that?’ ”

But the shutdown could surface in other legal challenges. Environmentalists wary of the Trump administration’s efforts to expand oil development in the Arctic have already warned the government is undermining legally required environmental analysis and consultation by holding public meetings when agency offices are closed and their websites are frozen.

That argument could be raised in future lawsuits challenging the administration’s rewrite of a plan for managing energy development in the 22.1-million-acre National Petroleum Reserve-Alaska.

Questions also have been raised about the Interior Department’s decision to process drilling permits either as an “exempted activity” or by tapping user fees. Antideficiency claims could be added to challenges of the underlying agency action, said William Snape, a fellow at American University Washington College of Law and senior counsel with the environmental group Center for Biological Diversity.

Legal Challenges