I do not spend much time looking at NOTAMs but I do not believe this type of wording is found with every NOTAM message. From what I have seen it is usually attached to NOTAMs pertaining to TFRs or security, as a way to establish authority. 49 USC is U.S. Code Title 49 (Transportation) and 14 CFR Chapter I is Code of Federal Regulations, Aeronautics and Space, FAA, DOT.