The short answer is yes they are broadly legal. for use and ownership Flamethrowers are not considered firearms by the ATF( Alcohol Tobacco and Firearms). There is no NFA tax stamps or federally licensed firearms (FFL) dealer required to buy, posses or sell. Flamethrowers are an unregulated tool and can be sold online and in person.
Some states have stricter rules. Maryland has a complete ban on flamethrowers and classify them under their "destructive device" code § 4-501(b)(2). But may be possessed by individuals with a 9,10,11 FFL license. California will allow flamethrowers but they have to be modified to to only spray 10 feet or less.
Flamethrowers can be shipped but it is the purchasers responsibility to comply with state and local laws, permits and licensees.
(This is general information, Vulcan Flamethrowers LLC. is not giving legal advice just passing on general information. This information can change so to stay up to date you (consumer) need to check you local ordnances and laws regarding this subject.)
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