"Whether the election can be postponed or not is a legal black hole," said Adam Winkler, a law professor at the University of California at Los Angeles. "There's very little precedent for such an act."
Federal law requires presidential elections to be held on the Tuesday after the first Monday in November, but it also provides that if a state "has failed to make a choice on the day prescribed by law, the electors may be appointed on a subsequent day in such a manner as the legislature of such State may direct."
In case of emergencies that threaten to disrupt voting, the federal Election Assistance Commission advises state election officials to "review existing State law to determine if the Governor has the power to cancel an election or designate alternative methods for distribution of ballots." - Politico
In other words, it is technically up to each State Legislature and Governor according to local election law. The Federal Government appears to have little say in directing the States, and there is no precedent for this. I really don't believe that any State wants to open up this can of worms, because if they do, the lawsuits will probably make Florida in 2000 look like a reasonable exercise in jurisprudence.
