Standing in the Brady briefing room at the White House last week, Donald Trump said that despite new restrictions on the number of journalists allowed in the room, there were still too many reporters around.

“You’re actually sitting too close,” the president told the journalists. “We should probably get rid of about another 75, 80% of you. I have just two or three that I like in this room.”

If it was a joke, the timing was terrible.

As the coronavirus crisis has grown, so too has the power of the president’s whim to shape American life, whether that means choosing which states get emergency medical equipment first, deciding where to deploy troops to build temporary hospitals – or controlling what the public knows about what the government is doing.

In recent weeks, Trump has invoked emergency powers enabling him to waive certain healthcare regulations and direct enormous streams of cash to areas of need. He has also announced that the federal government would use its authority to direct private companies to boost the production of surgical masks, gloves and other equipment, although the status of those efforts was unclear.

For now the risk – the seeming surety – of a national disaster has fostered a willingness in even Trump’s harshest critics for him to aggressively seize the reins of his office and marshal the power of the federal government toward a muscular and decisive response that could save thousands of lives.

But with this widespread desire for action has come related concerns about where, exactly, that power will stop growing, when the emergency crests, and how that power will shrink when the crisis subsides.

Civil society advocates warn the fog of crisis could give Trump cover to grab adjacent powers, not related to the current emergency, that might be difficult to claw back – especially if Congress and the courts failed to check Trump after the fact.

“Ordinarily, that’s not something you’d be worried about, because it would seem kind of unthinkable for a president to exploit a pandemic to arrogate a bunch of power that he doesn’t need,” said Elizabeth Goitein, co-director of the liberty and national security program at the Brennan Center for Justice.

“But we have seen that this president is willing to abuse emergency powers, and to use them for political gains. And so we have to worry.”

By invoking the National Emergencies Act on 13 March, Trump gained access to emergency powers in more than 100 other statutes, Goitein said, “and if you look at those authorities, very few of them relate to health crises”. With incremental action, Trump could expand government control of the internet, freeze private assets or change the size and composition of the armed forces.

Other steps Trump has taken in the coronavirus response, such as restricting international borders and imposing mandatory quarantines for certain travelers, do not rely on emergency authorities but could create a legacy of expanded executive power that advocates fear could outlast the virus.

One step Trump did not take after his administration declared a public health emergency on 31 January was to reallocate funds to speed approval for drugs and ramp up the production of coronavirus tests kits. Trump’s failure to deploy that power, the University of Texas law professor Steve Vladeck said, may have ironically created a scenario in which he ends up using much broader powers.

“The president’s dilatory use of the powers he has, I think, is going to end up requiring him to use a lot more of that power, in ways that are a lot more controversial and a lot more coercive and a lot more inconsistent,” Vladeck told Benjamin Wittes of the Brookings Institution in a Lawfare podcast about emergency powers and coronavirus.

Members of the Maryland national guard control entry to a section of parking lot on the south side of FedEx Field on Monday that officials said will become a clinic for coronavirus health screenings. Photograph: Chip Somodevilla/Getty Images

Concerns that the administration would look for ways to use the crisis to move the lines of the law were sharpened by reports last week that the justice department had asked Congress to pass legislation allowing federal judges to detain people indefinitely without trial during emergencies.

But analysts differ in their imaginations of how a dangerous expansion of power by Trump might unfold, with the economy in a tailspin and a presidential election on the horizon.

Under extraordinary powers accessible to Trump after his national emergency declaration, he could declare the coronavirus to be a “foreign threat” and impose financial sanctions on anyone he said was contributing to the threat, such as a media company or a political opponent.

He could announce an interstate travel ban, enforceable by the military, citing a need to stop the spread of the virus. Along similar lines, he could take steps that could make it harder for some people to vote in the presidential election in November – or make it more difficult for legal challenges to such steps to be heard in court.

“It’s not hard to imagine the federal courts in general, and this supreme court in particular, being remarkably deferential to the federal government in a public health crisis like this one,” Vladeck told Wittes.

Or, in what analysts describe as a worst-case scenario, the justice department could move for a federal judge to declare a breakdown of local law enforcement – at which point Trump could theoretically deploy the military in the streets, in a manner breaking with past deployments of active-duty troops for disaster response.

As an ominous reference point, civil liberties advocates point to anti-democratic moves taken by the Israeli prime minister, Benjamin Netanyahu, to close most courts, adjourn parliament and exploit secret cellphone data.

“We have to be on the lookout for any use of these powers that goes beyond what public health experts are recommending as necessary, and that intrude on civil liberties,” Goitein said.

In offhand comments, Trump has occasionally expressed a reticence about the power of his office, which he elsewhere has described as unlimited.

“A lot of executive power, if we don’t have to use it that would be a good thing, not a bad thing,” he said at the White House last week. As late as Wednesday, Trump was resisting calls to invoke the Defense Production Act to get private businesses involved in mask and ventilator production, saying, “We hope we’re not going to need it.”

Donald Trump’s track record offers no reason to believe that he will eagerly accede to the contraction of powers that expanded in a time of emergency response, experts warn. Photograph: Eric Baradat/AFP via Getty Images

The Berkeley law professor John Yoo, who crafted legal cover for torture programs in the George W Bush years, took a sanguine view of Trump’s power and its containment.

“There’s not a whole lot more I think that the president can do, unless we saw something much more serious occur such as the breakdown of law and order,” said Yoo in a call-in forum hosted on Friday by the Federalist Society. “Even then the president would need to rely on the request of state governors for assistance before he could intervene.”

But Trump’s track record offers no reason to believe that he will eagerly accede to the contraction of powers that expanded in a time of emergency response, said Goitein, of the Brennan Center.

“If you divorce his emergency orders from the context of every other thing he’s ever said or done, you might be able to believe that,” she said. “But if you put it in the context of a president who has said that article II gives him the power to do anything he wants, and a president who has ordered officials not to comply with congressional subpoenas, and a president who has said that Congress does not have the authority to impeach him – then I think you absolutely have to be worried.”