The majority of administrative regulations are issued by the Department of Homeland Security (DHS), the Executive Office for Immigration Review (EOIR), the Department of Justice, the Department of Labor, and the Department of State.
Code of Federal Regulations: Title 8 of the CFR addresses "Aliens and Nationality".
On Westlaw, the administrative decisions of a number of agencies can be found under Practice Areas > Immigration > Administrative Decisions & Guidance. On Lexis, go to Practice Area or Industry > Immigration > All Immigration Law Administrative Materials.
Board of Immigration Appeals (BIA) Decisions:
Administrative Appeals Office (AAO) (formally the Administrative Appeals Unit (AAU)) Decisions:
OCAHO Decisions (Immigration-related decisions issued by the Chief Administrative Hearing Officer of the Department of Justice):
Board of Alien Labor Certification Appeals (BALCA) Decisions: