The Covid-19 pandemic has sent people streaming to History in search of previous events to provide some guidance for the present. Applying to America the understanding of the impact of epidemic disease formulated by his Yale colleague Frank Snowden, law professor John Fabian Witt argues that “New germs help make new laws and institutions, yet old ways of doing things shape the course of epidemics and the ways in which we respond to them.”
Witt discerns two trends in the American government response to disease, beginning with the smallpox epidemic that coincided with the Revolutionary War. One is the development of preventive measures. These measures include things like draining marshes and bogs to rob mosquitoes carrying malaria, yellow fever, and dengue of their habitat; providing city populations with clean water to drink and to clean the filth off the streets in order to avoid cholera; and the screening of populations to prevent the transmission of disease. Government, what Witt calls the “Sanitationist State,” grew in power in response to the need to prevent disease. At the same time, science and medicine advanced rapidly in their ability to provide government with the needed tools. All of these efforts Witt sees as expressing liberal values of a free society.
In contrast, there are the coercive or authoritarian measures of a “Quarantinist State.” Governments caught up in a desperate emergency may impose an “authoritarian and discriminatory control over people of color, the poor, and immigrant newcomers.” Here it is hard not to think that Witt may be using epidemic disease chiefly as a metaphor to criticize other forms of expanded government power. “America’s record on infectious diseases is filled with discrimination and authoritarianism….Each new infection presents a risk of entrenching existing inequities.” The same might be said of any national security emergency. Witt may be extending an earlier argument against John Yoo’s interpretation of the Constitution in the aftermath of the undoubted emergency created by 9/11. However, one could just as easily point to the USA Patriot Act and the revelations of Edward Snowden for further examples of what can happen under an “emergency” that never seems to end.
Witt raises vital issues. A democracy is rule by laws, not by men. A democracy’s laws define the operations of government during normal times. An emergency is a departure from what is normal. What becomes of the rule of law during an emergency? Can the courts grant broad discretion to government officials to deal with an emergency? When should government officials surrender such discretionary power? Is it fair to judge the quality of a democracy by what it does in an emergency, rather than by what it does in normal times?
Happily, American presidents have always pulled back or were pulled back from the brink in previous emergencies. Those were decisions taken by individual men. We know less about the behavior of the career bureaucrats who operate the machinery of government.
 See, for example, John Fabian Witt, American Contagions: Epidemics and the Law from Smallpox to Covid-19 (2020), reviewed by Adam J. White, WSJ, 10 November 2020.
 The case of “Typhoid Mary: in 19th Century New York City offers a revealing example.
 War, rebellion, natural disasters, and epidemic or pandemic outbreaks of disease are common examples of conditions which may justify declaring a “state of emergency.”
 Declaring a “state of emergency” or a “state of siege” is a common feature of anti-democratic coups.