Extra Help was enacted into law with the passage of the Medicare Modernization Act. You can look up the actual statutory provisions of the MMA that govern Extra Help in Section 1860-D-14 (42 United States Code 1395w-114).
Regulations are the legal interpretation of the statute by the governmental agency in charge of administering a statute.
In the case of the Medicare drug coverage, the Centers for Medicare & Medicaid Services (CMS) administers the statute, and the Extra Help regulation is found in Volume 20 of the Code of Federal Regulations, Part 418 (20 CFR Part 418).
When a regulation is proposed by a federal agency, the public is given an opportunity to comment, and the comments are published in the Federal Register, along with the response of the federal agency. You can see the comments that were submitted on the proposed Extra Help regulation and how Social Security responded in making the regulation final.
70 Federal Register Page 77644 (December 30 2005) (185Kb PDF file)
Social Security Policy
The Social Security Program Operation Manual System (POMS) contains Social Security’s policies and procedures. In the POMS, Social Security details its procedures and policies. Extra Help eligibility, applications, redeterminations and appeals policies and procedures are here: Chapter HI 030.