NFPA are recommendations
UNTIL they are incorporated into legal code by local, State or Federal rule, then they are enforceable by law.
The number of citations against a NFPA codes are enormous. Many of the NFPA codes are adopted by legal entities so they do not have to write their own codes. Most of the NFPA codes are adopted by rule so the States do not have to write their own and just point to NFPA. Even OSHA and EPA does the same pointing to NFPA as incorporated rule. OSHA points to NFPA for a lot of enforceable codes such as NFPA 70 NEC, 70E Arc Flash, 101 Life Safety Code and so on. The real problem is the focus is on NFPA 495 "explosive materials" but the storage of smokeless powder in personal residence is included within the adopted rule. Unless it is specifically carved out by a State which may be the case in some isntances where the point is for fireworks, there doesn't seem to be an easy out. At least not one I could find and I have looked real hard over the years for it.
If anyone can find an exception to NFPA 495 for storage of residential smokeless powder that has been adopted by total rule by a State, please chime in.
NFPA 495 Explosive Materials code is adopted by rule by a lot States relative to fire safety through the Fire Marshal. Just go to your state fire marshal site and it will probably be there. They use it to control fireworks mostly but the residential storage of smokeless powder is in it as well.
What is interesting is BATF does not include smokeless powder in THEIR Explosive Materials rules and this is off their website:
Is smokeless powder designed for use in small arms ammunition subject to the explosives storage requirements?
Smokeless powders designed for use in small arms ammunition are exempt from regulation under 18 U.S.C. Chapter 40 and the regulations in 27 CFR Part 555. Packaging that readily identifies the smokeless powder as being designed for use in small arms ammunition may help in determining whether it is entitled to the exemption. Smokeless powder designed for use other than in small arms ammunition, and explosive products such as squibs, fireworks, theatrical special effects, or other articles that may contain smokeless powders, are regulated and must be stored pursuant to the regulations at 27 CFR 555, Subpart K ā Storage.
It should be noted that persons engaged in the business of importing or manufacturing smokeless powder designed for any use must have a Federal explosives license. Further, importers of smokeless powder designed for use in small arms ammunition must also possess an ATF firearms importers license (Type 08 or 11); must register with ATF under the provisions of the Arms Export Control Act; and must submit (to ATF) and receive an approved ATF Form 6 ā part I (5330.3A), Application and Permit for Importation of Firearms Ammunition and Implements of War.
For Example - OSHA - Incorporated by Reference Link;
OSHA Incorporated by Reference
The list is a very long list of those "non legal codes" incorporated by reference and now enforceable.