Title 15, Chapter 22 of the United States Code deals with trademark law.
See the Gallagher guide on U.S. (Federal) Laws for print and online sources of the U.S. Code.
Title 37, Parts 2, 3, 6, and 7 of the Code of Federal Regulations deal with trademarks.
The Trademark Manual of Examining Procedure (TMEP) is published to provide trademark examining attorneys in the United States Patent and Trademark Office (USPTO), trademark applicants, and attorneys and representatives for trademark applicants with a reference work on the practices and procedures relative to prosecution of applications to register marks in the USPTO. The manual contains guidelines for examining attorneys and materials in the nature of information and interpretation, and outlines the procedures which examining attorneys are required or authorized to follow in the examination of trademark applications.
See the Gallagher guide on U.S. Administrative Law Research for information on print and online sources of the Code of Federal Regulations, the Federal Register, and other related sources.
The website of the U.S. Patent and Trademark Office maintains a page with current and proposed regulations.
U.S. Patent & Trademark Office (USPTO)
Trademark Trial & Appeal Board (TTAB)
Commissioner of Trademark & Patent