The FDA sent Walmart a letter in early April, asking the retailer to submit a plan of action to mitigate illegal tobacco sales.
Under the legislation, any sale — in-store and online — of an e-cig that has not undergone an FDA review would be prohibited.
Monday's action is part of a broader push by the FDA to reduce youth smoking.
The head of the Food and Drug Administration is questioning whether electronic cigarette maker Juul and its new partner Altria are following through on pledges to help stop underage vaping.
The FDA chief reminded the two companies of the “independent responsibility” they have to address the “epidemic” of youth vaping.
Altria and Juul struck a $12.8 billion deal on Thursday.
How Juul became a $38 billion company in a flash.
Altria is spending $12.8 billion for a stake in e-vapor company JUUL as one of the world's biggest tobacco companies tries to offset declining cigarette use.