Governors are starting to close their borders. The implications are staggering.

The coronavirus pandemic is testing the very notion that the United States are united.

Texas Gov. Greg Abbott (R) signed an executive order on Thursday that would require travelers from some coronavirus hotspots to self-quarantine: It provides that “every person” who flies into Texas from “New York, New Jersey, Connecticut, or the City of New Orleans, or in any other state or city as may be proclaimed hereafter, shall be subject to mandatory self-quarantine for a period of 14 days from the time of entry into Texas or the duration of the person’s presence in Texas, whichever is shorter.”

Other states have imposed similar orders. Florida Gov. Ron DeSantis (R) imposed an order on Tuesday that requires anyone flying from New York, New Jersey, or Connecticut to self-isolate for 14 days. Alaska and Hawaii also imposed self-quarantine orders on people traveling from other states.

These orders implicate one of the fundamental premises of the union among the 50 states: the right of American citizens to travel among them freely.

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