Precedent says West Virginia teacher's strike isn't lawful

West Virginia teachers spent a third day on strike on Feb. 26 after negotiations over the weekend were insufficient to end the walkout. But is their strike legal?
Shortly before the strike began, state Attorney General Patrick Morrisey (and U.S. Senate candidate) said it wasn’t.
On Feb. 21, Morrisey tweeted, " 'The impending work stoppage is unlawful and should come to an end.' — Patrick Morrisey."

Source: politifact