I don't know about a law. RVIA does list some standards. From their website:
Fire & Life Safety Requirements as specified in NFPA 1192 Standard for RVs.
Interior finish flame spread limitations are required.
Minimum exit facilities providing unobstructed travel to the outside of the vehicle must be available.
Smoke alarms, Fire extinguishers, CO alarms and Propane detectors are mandate based on applicable criteria.
Maybe if you followed up with them or checked the NFPA 1192 they reference you could gain some more info.
ClickyFor those worried about the height, I read a thread a while back where a poster said they put their picnic table under the window to climb down on in case of emergency. Don't shoot the messanger :)