standards/codes/laws - NFPA develops minimum standards for pretty much anything relating a situation that could create a fire, or deals with a fire. Within each and all of these standards is a statement to the effect that they are the minimum recommended for safety, and their adoption/implementation is subject to the Local Authority Having Jurisdiction. The 'local' AHJ can be city, county, or state. The only time the Federal gov't gets involved is with regard to properties they own/occupy, or in some case how their money is spent. Example - a nursing home receiving Medicaid/Medicare payments for their residents can be required to retro-fit a fire sprinkler/alarm system as a life safety consideration, if they want to continue receiving federal funds.
In the late 90's the 4 major code creation groups, ICBO (Int Conference of Bldg Officials, source of the Uniform Codes), BOCA (Bldg Officials Conference of America), SBC (Southern Bldg Conference), and another who's name I can't remember consolidated their organizations into the International Codes Council in an effort to standardize building codes nationally, rather than the regional approach that was in place at that time. Their first published set of standards was in 2000, and as leaders in all aspects of building standards they are in fact adopted in many areas worldwide that do not have the knowledge resource to create their own standards.
At that time most all conferences paid NFPA for publication rights to their standards, and then included them in their standards with certain adjustments they felt were needed to meet their requirements. There was also discussion between ICC & NFPA about a degree of consolidation that would incorporate the entire NFPA collection into the ICC. Due to an inability to agree regarding specifics of fire protection systems standards, that didn't occur, and while on most items relating to fire protection the ICC references the NFPA standards, NFPA actually created their own building code NPFA 5000. While the ICC codes are the dominant standard, many states have adopted NFPA 5000 as their building code.
Regardless of what building code is being used, they only become law based on adoption by statute of the AHJ. That can be your city, county, or state depending on the specific geographic location, and in some cases the type of occupancy. ie a hospital is most likely subject not only to the city/county standards that have been adopted, but to state standards as they generally set minimum guidelines for health care.
Offered for clarification based on 35+ years in the fire protection industry dealing daily with NFPA standards & building codes/officials. With the exception of national security, and federal facilities, codes/laws are adopted/applied from the State down to the City level. Oh yes, the NEC is something of a misnomer, in that it's not a Code or law until adopted as such in writing. The 'National' aspect of the name refers to it's creation by the National Fire Protection Association, not creation or adoption by the federal gov't.