“This is, I think, pushing the envelope quite a bit and is highly counterproductive,” Lawrence O. Gostin, a professor of global health law at Georgetown University, said. “I can’t think of a situation where any jurisdiction in the United States in modern times has simply quarantined a whole class of people.”

In a new era of mass travel and global pandemics, public health officials have seen the utility of quarantines to rein in outbreaks that appear to be spiraling out of control. But the approach, experts said, is an extreme one.

“It doesn’t seem like we’re to that stage yet,” Steven D. Gravely said, a lawyer who helped Virginia rewrite its laws on quarantine to make it easier for the state to respond quickly to disease outbreaks. Instead, he said, “there’s so much anxiety right now, that’s become the problem.”

Government officials, he added, need to explain “why are you doing this, what do you hope to accomplish. Because otherwise people read into it things that are not there.”

The power to impose quarantines derives from the general police power granted to states in the Constitution. But over the last century, state and federal authorities have moved away from broadly quarantining categories of people, said Mr. Gostin, adding that one would have to reach back to the influenza pandemic of 1918 to begin to find the sort of blanket approach being employed in response to Ebola in New Jersey.

General quarantines, seen as having only limited effectiveness even when employed against the flu a century ago, fell out of favor as antibiotics and other treatments were developed to more directly address the contagious without affecting those who might have been exposed but display no sickness.

At the height of the AIDS epidemic, quarantines were supported in some quarters, but no such measures were ever adopted. Similarly, there were no quarantines in the United States during recent pandemics of H1N1 or SARS.