President Joe Biden has issued a series of executive orders—without express legislative authority—mandating vaccination or weekly testing for a significant percentage of American workers. Since the announcement, I have been besieged with calls, emails and media requests all asking the same question: is it constitutional? Fortunately, I've just completed writing a book on precisely that subject, entitled The Case for Vaccine Mandates, in which I analyze the legal issues surrounding vaccination, masking and related mandates.

Here is my conclusion: it depends!

It depends on the following three questions, all raised by Biden's actions:

1) Does the federal—as distinguished from state—government have jurisdiction over COVID and vaccine mandates?

2) If the federal government has (or shares) such jurisdiction, may it constitutionally require, even with exceptions, workers to be vaccinated against their will or as a condition of their employment?

3) If the federal government has the constitutional power to mandate such vaccinations, can that order be made by the executive, as distinguished from the legislative branch of the federal government?

Unless all three questions are answered in the affirmative, President Biden's orders would not pass the test of constitutionality.

The first question is easy. Yes, the federal government has jurisdiction over America's response to a pandemic that does not recognize state boundaries. So do the states, but the supremacy clause of the Constitution has been interpreted to mean that where there is joint jurisdiction, and a conflict between federal and state law arises, federal law prevails.

The second question is harder, but courts would likely sustain a properly enacted law, with appropriate exceptions, that mandated vaccination as a last resort. There is a Supreme Court decision on compelled vaccinations, but it is a 1905 state case that carried a small fine for noncompliance. Subsequent lower court decisions point in the same direction. So it is likely that a properly enacted statute mandating vaccination or conditioning employment and other benefits on vaccination or testing would be upheld.

WASHINGTON, DC - SEPTEMBER 09: U.S. President Joe Biden speaks about combatting the coronavirus pandemic in the State Dining Room of the White House on September 9, 2021 in Washington, DC. As the Delta variant continues to spread around the United States, Biden outlined his administration's six point plan, including a requirement that all federal workers be vaccinated against Covid-19. Biden is also instructing the Department of Labor to draft a rule mandating that all businesses with 100 or more employees require their workers to get vaccinated or face weekly testing.Kevin Dietsch/Getty Images

That brings us to the third question—can such a sweeping "emergency" mandate, that is not limited in time, be authorized by the president without explicit legislation by Congress? That is the most daunting question of all. It is daunting because the constitutional authority of the presidency has been expanding since the New Deal and its limits are constantly being tested by presidents of both parties. This is evidenced by the wars we have fought in recent decades without a congressional declaration of war, and more recently by Donald Trump's border wall and Biden's vaccine mandate.

Presidents generally cite broad and vague congressional authority for their actions. Sometimes the courts accept this authority, and sometimes they don't. In this case Biden is relying on the Occupational Safety and Health Act (OSHA) from 1970. It was intended to protect workers against unsafe or unhealthy workplaces. Although it does not expressly cover compelled vaccinations or testing, OSHA's language may be general enough to allow the courts to conclude that it authorizes such emergency protective measures. Even if it does, OSHA requires that certain steps be taken before emergency measures are enforced. It would surely have been better if Congress had explicitly authorized the mandates—better for democratic values and easier as a matter of constitutional law.

One point is clear: both sides are exaggerating their constitutional claims. Some proponents of the Biden mandate assure us that its constitutionality "is completely clear," while some opponents are certain that it is "utterly lawless." The reality is that the question could go either way. In such a close case, President Biden is justified in doing what he believes to be in the public interest and leaving it to courts to decide. That is what FDR did in the 1930s. The situation would be different if it were clear that Biden's actions were unconstitutional, and he knew it: the president has sworn to uphold the Constitution and may not act in a clearly unconstitutional manner and leave it to the courts. But that is not the case here; these are close questions, and the courts might well uphold the Biden mandate.

There will be immediate challenges—from workers, employers and states—to the Biden mandate. Courts will be asked to enjoin its enforcement. Emergency applications will be made to the Supreme Court. So stay tuned. It's far from over.

Follow Alan Dershowitz on Twitter @AlanDersh and on Facebook @AlanMDershowitz. His new podcast, The Dershow, can be found on Spotify, YouTube and iTunes.

The views expressed in this article are the writer's own.