I do not see how, even with Biden as POTUS, the US will stop COVID-19

[Celerity]

62. massive powers are unleashed is a POTUS declares a state of national emergency

That said, martial law was probably not the best subject to toss out in the OP, as it is such a loaded term.

This article was directed at things to worry about with Trump, but is applicable to any POTUS.

The Alarming Scope of the President's Emergency Powers



https://www.theatlantic.com/magazine/archive/2019/01/presidential-emergency-powers/576418/

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But will they? Unknown to most Americans, a parallel legal regime allows the president to sidestep many of the constraints that normally apply. The moment the president declares a “national emergency”—a decision that is entirely within his discretion—more than 100 special provisions become available to him. While many of these tee up reasonable responses to genuine emergencies, some appear dangerously suited to a leader bent on amassing or retaining power. For instance, the president can, with the flick of his pen, activate laws allowing him to shut down many kinds of electronic communications inside the United States or freeze Americans’ bank accounts.

Other powers are available even without a declaration of emergency, including laws that allow the president to deploy troops inside the country to subdue domestic unrest. This edifice of extraordinary powers has historically rested on the assumption that the president will act in the country’s best interest when using them. With a handful of noteworthy exceptions, this assumption has held up. But what if a president, backed into a corner and facing electoral defeat or impeachment, were to declare an emergency for the sake of holding on to power? In that scenario, our laws and institutions might not save us from a presidential power grab. They might be what takes us down.

1. “A LOADED WEAPON”

The premise underlying emergency powers is simple: The government’s ordinary powers might be insufficient in a crisis, and amending the law to provide greater ones might be too slow and cumbersome. Emergency powers are meant to give the government a temporary boost until the emergency passes or there is time to change the law through normal legislative processes. Unlike the modern constitutions of many other countries, which specify when and how a state of emergency may be declared and which rights may be suspended, the U.S. Constitution itself includes no comprehensive separate regime for emergencies. Those few powers it does contain for dealing with certain urgent threats, it assigns to Congress, not the president. For instance, it lets Congress suspend the writ of habeas corpus—that is, allow government officials to imprison people without judicial review—“when in Cases of Rebellion or Invasion the public Safety may require it” and “provide for calling forth the Militia to execute the Laws of the Union, suppress Insurrections and repel Invasions.”

Nonetheless, some legal scholars believe that the Constitution gives the president inherent emergency powers by making him commander in chief of the armed forces, or by vesting in him a broad, undefined “executive Power.” At key points in American history, presidents have cited inherent constitutional powers when taking drastic actions that were not authorized—or, in some cases, were explicitly prohibited—by Congress. Notorious examples include Franklin D. Roosevelt’s internment of U.S. citizens and residents of Japanese descent during World War II and George W. Bush’s programs of warrantless wiretapping and torture after the 9/11 terrorist attacks. Abraham Lincoln conceded that his unilateral suspension of habeas corpus during the Civil War was constitutionally questionable, but defended it as necessary to preserve the Union. The Supreme Court has often upheld such actions or found ways to avoid reviewing them, at least while the crisis was in progress. Rulings such as Youngstown Sheet & Tube Company v. Sawyer, in which the Court invalidated President Harry Truman’s bid to take over steel mills during the Korean War, have been the exception. And while those exceptions have outlined important limiting principles, the outer boundary of the president’s constitutional authority during emergencies remains poorly defined.

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