Read: How the pandemic will end

Other countries, including Western democracies such as Italy, Spain, and France, are following China’s lead, locking down entire regions or the nation as a whole. India’s prime minister, Narendra Modi, decreed a 21-day lockdown for 1.3 billion people, the largest cordon sanitaire in world history.

Meanwhile in the U.S., where COVID-19 cases are skyrocketing, the approach has been more piecemeal. Many states and localities have ordered businesses, schools, and workplaces to close and limited the number of people that can gather in public. At least 24 states have directed all residents to shelter in place, or stay home. But other states have allowed businesses such as bars and restaurants to remain open to the public, or let their school districts decide whether to close schools. Why has America failed to take more aggressive national action?

President Donald Trump has expressed inconsistent intentions for a national, or even regional, lockdown. On March 24, eager to avoid further economic and social harms arising from business closures and other key physical-distancing measures, the president stated that the U.S. should be open for business by April 12. Finally swayed by warnings from public-health experts that lifting restrictions too soon could cause far more deaths, he has now extended that timeline to the end of April. Then on March 28, Trump said he might order a two-week quarantine of New York, New Jersey, and parts of Connecticut. Such an order would have restricted the movement of millions of Americans, even in areas with low COVID-19 risk, and could have backfired if it incited mass migrations. However, faced with questions on legal enforceability, Trump backed away from the mass quarantine, and instead the Centers for Disease Control and Prevention (CDC) issued a domestic-travel advisory for the area, asking residents of the three states to refrain from nonessential domestic travel for 14 days.

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Even if the president desired to take stronger action, America’s national-level response would be hampered in part by its federalist system. Constitutional authority for ordering major public-health interventions, such as mass quarantines and physical distancing, lies primarily with U.S. states and localities via their “police powers”—a drastic difference from the national authorities of countries such as China and Italy. Still, the federal government does have narrow authorities to reduce the spread of COVID-19, which are most expansive at the U.S. border. Trump has, for example, banned the entry of foreign nationals who have traveled in many of the world’s regions, including China and most of Europe, within 14 days before their arrival to the U.S. More recently, the president closed America’s borders with both Mexico and Canada. Congress has exclusive constitutional power to regulate interstate commerce and could restrict travel among the states, but the president cannot, unless Congress provides statutory authority. The CDC, as an executive agency under the Department of Health and Human Services, holds limited regulatory authority to issue quarantines, but lacks the authority to ban interstate travel outright. Even during the Zika outbreak, the CDC only recommended that pregnant women avoid travel to southern Florida; it did not issue any order.