The state describes it as a "flexible, case-by-case approach"

California ordered a 21-day quarantine Wednesday for travelers who have had contact with confirmed Ebola patients.

The state said the quarantine order requires local counties to individually assess people at risk for Ebola and assign an “appropriate level of quarantine.” Those who are at a high risk, defined by the state as people who had contact with an Ebola patient, will be put in a 21-day quarantine.

“Although quarantine can involve isolation at home, it may be tailored to allow for greater movement of individuals who are deemed to be at lower risk,” the California Department of Public Health said.

California’s move follows similar quarantine orders from New York, New Jersey and Illinois, measures that have been criticized by health experts—and by President Barack Obama—as putting fear over science and potentially hampering efforts to contain the outbreak that has killed thousands in West Africa by making it harder for aid workers to travel there and back.

The state said local health officials have the authority to order the quarantine of people who may have an infectious disease that’s a public health threat.

“This flexible, case-by-case approach will ensure that local health officers throughout the state prevent spread of the disease,” the department said, “while ensuring that individuals at risk for Ebola are treated fairly and consistently.”