GovInfo is the online presence of the Government Publishing Office (GPO). It is an excellent- and free! - choice to use for locating federal primary law (case law, statutes, and administrative regulations) and other materials published by our federal government.
This legislative information Web site of the Library of Congress provides access to federal legislation and related documents. It is a great source for compiling legislative histories and a good first stop to check for major pieces of legislation currently in the news.
This site's self-proclaimed purpose is to function as a clearinghouse for information about the U.S. federal court system. Along with links to succinct explanations of the roles of the different courts, its hompage features an informative news feed about the courts' business.
The Federal Register, published daily, contains rules and regulations (proposed and final) of federal executive branch agencies, as well as notices and other related materials. Executive orders and other documents issued by the president are also published in the Federal Register.
The Code of Federal Regulations (CFR) contains the subject-arranged collection of current final rules and regulations of the federal executive agencies. NOTE: This electronic version is no more current than the print version of the Code. You must check for updates via the eCFR. (https://www.ecfr.gov/cgi-bin/ECFR?page=browse)
This is the online presence for the Ilinois state court system. Scroll over the blue "Courts" tab to find direct links to the homepages for the Supreme, Appellate, and Circuit courts. Scroll over the neighoring "Documents" tab to find a link to state Supreme and Appellate court opinions.
The State of Illinois homepage is aimed at citizens in general, but can also be a good starting point for research on Illinois administrative law. Look at the dropdown box for the "Directories/Contacts" option under "Quick Reference" for a link to a list of state agencies. Use the links on that list to access the agencies' pages, which often contain their rules and decisions.