Several executive orders signed by President Donald Trump order a freeze of federal funds that Congress has already approved. But, according to both the Constitution and something called the Impoundment Control Act of 1974, the president does not have the authority to do that unilaterally.

For a chaotic, confusing couple of days last week, it looked like the Trump administration was about to halt federal spending on all sorts of programs — including, possibly, housing vouchers, low-income heating assistance, Medicaid and Head Start.

But after widespread outrage, lawsuits and two court orders, the Office of Management and Budget rescinded its memo ordering that spending freeze.

“Congress authorized that money to be spent, and it is not up to the president to decide, ‘I don’t want to spend it,’” said Sally Katzen, a professor at New York University’s School of Law.

The Constitution gives Congress what’s called “the power of the purse” and not the president, Katzen said. “And that means that when Congress has appropriated funds, they should be spent on what Congress had in mind.”

In addition to the Constitution, David Super at Georgetown Law School said there’s also the Impoundment Control Act of 1974.

“The Impoundment Control Act was something that Congress passed during the Nixon administration to deal with his desire to impound, or refuse to spend, money that Congress had directed him to spend,” he said.

Much like Trump, President Richard Nixon didn’t want to spend money on certain social and environmental programs that Congress had approved, so he just refused to spend it.

“He was sued over that. He lost all the cases that were decided on the merits, including 9-0 in the Supreme Court,” Super said. “But Congress decided to pass a law giving him a legitimate path to propose impounding, or not spending, money.”

That law — the Impoundment Control Act — says that if the president doesn’t want to spend money on, say, food stamps, upgrading infrastructure or foreign aid for whatever reason, he must go back to Congress and ask them to reconsider.

So far, Trump hasn’t done that.

Even though OMB rescinded its now-infamous memo last week, the administration is currently withholding certain funding — including for green energy projects and foreign aid, according to Samuel Bagenstos at the University of Michigan Law School.

“All of this was based on the same theory that President Trump wants to decide if this spending is consistent with his policy preferences,” he said. “And that’s not something that is a proper reason under our Constitution and laws to pause or withhold spending that Congress has adopted.”

At a press conference House and Senate Democrats held Monday afternoon, Representative Ilhan Omar, of Minnesota called the president’s withholding of funds a Constitutional crisis.

“We have the power of the purse,” she said. “We get to decide where money is allocated, and it’s the executive’s power to make sure that that money gets to where it needs to get.”

Right now, that’s not what’s happening.