Searching the Civil Rights area may bring to light useful information not found in the environmental material. They are updated more frequently and have annotations. There are copies of all three of these titles in the Reading Room, and on the Fifth Floor in the Federal Materials section. Current state statutes are available on Lexis and Westlaw. Missouri on the fifth floor, and other states on the first floor.
Previous editions are in the stacks.
Another place to search is LegalTrac . Journals occasionally review state laws in a particular area. The Lexis and Westlaw links above will also provide access to federal and state environmental case law. The Federal, regional, and Missouri reporters are on the fifth floor. Digests for Federal and Missouri are in the Reading Room.