Below are two articles concerning the general legality of prescribing
Legal aspects of providing naloxone to heroin users in the United States, by Scott Burris, Joanna Norland, and Brian R. Edlin, International Journal of Drug Policy
Some states have passed specific naloxone access laws with the intention of preventing overdose
The Network for Public Health Law has compiled a summary of these laws titled Legal Interventions to Reduce Overdose Mortality. Importantly, third party prescribing is authorized in Washington, Massachusetts and Illinois (in IL, third party prescribers must register)- click on the states to see specific legislation.