Good links to aviation materials are posted by Landings and the Dowling College Library.
U.S. Laws: The relevant Federal and state statutes, Federal regulations, Department of Transportation cases, etc., are compiled in the CCH Federal Aviation Reporter. See "Federal Aviation Administration" for more on FAA regulations, decisions, etc.
Foreign Law: The Air Transport volume of the Getting the Deal Through series summarizes the laws of over 40 foreign countries. To find more resources, see "Foreign Laws," or the entry for the particular country.
International Law: International aviation is regulated by the International Civil Aviation Organization, which was created by the the Chicago Convention on International Civil Aviation.
The ICAO posts other relevant treaties in its Treaty Collection and a treaty index called the Database of Aeronautical Agreements and Arrangements.