UNIFORM COMMERCIAL CODE (UCC)
The Uniform Commercial Code is a body of model legislation governing commercial transactions. The UCC has been adopted in some form by all 50 states and Washington, DC. To find a state's version of the UCC, check its legislative code (look in the index for UCC).
For further information on the UCC, see this guide's UCC page.
OTHER STATUTES
State and federal jurisdictions have also codified various other aspects of contract law, such as those relating to consumer protection and government contracts. Legislative codes are available in annotated (containing editorial notes and research references) and unannotated (text of the law only) versions.
Each federal and state code set has an index. To locate relevant statutes, choose one of the annotated codes and search its index for your keywords.
FEDERAL STATUTES
United States Code - Official, unannotated version
Also available online at GPO's FdSys (free)
United States Code Annotated (USCA) - Westlaw's annotated version
Also available on WestlawNext
United States Code Service (USCS) - Lexis' annotated version
Also available on Lexis and Lexis Advance
STATE STATUTES
To find statutory codes for individual states, visit Lexis or Westlaw. Current, official, unannotated versions may also be found on state legislatures' websites.
The Law Library has some state codes in print. Check Scholar OneSearch or ask a librarian.
Massachusetts' code may be found here:
General Laws of Massachusetts - Official, unannotated version
Also available (unofficially) online from the Mass. Legislature
Massachusetts General Laws Annotated - Westlaw's annotated version
Also available on Westlaw and WestlawNext
Annotated Laws of Massachusetts - Lexis' annotated version
Also available on Lexis and Lexis Advance
For comparative state laws on contracts, consult:
Subject Compilation of State Laws and do a subject search for Contracts, Breach of Contract, Uniform Commercial Code, and related terms
Available via HeinOnline (research database)
FEDERAL CASES
STATE CASES
FEDERAL REGULATIONS
Also available online via GPO's FDsys (free, annual edition as it appears in print), e-CFR (free, unofficial, updated frequently) and on Westlaw, WestlawNext, Lexis and Lexis Advance
STATE REGULATIONS
Massachusetts regulations may be found here:
Also available via the Social Law Library (Legal Research database), Westlaw, WestlawNext, Lexis and Lexis Advance
Other state administrative codes may be found on Lexis and Westlaw.