The Food and Drug Administration (FDA) is moving fast to close off what seems to be the last remaining legal option for vaping companies that want to provide the e-liquid flavors that former smokers overwhelmingly prefer. Exercising regulatory authority that Congress recently gave it, the FDA has set a May 14 deadline for seeking "premarket" approval of vaping products that deliver nicotine derived from sources other than tobacco. Companies that fail to submit applications by then, the agency warns, "will be subject to FDA enforcement."