Final answer:
The resource that is used by judges as a reference in deciding contract cases, which summarizes and organizes the principles of contract law as developed by courts in the United States, is the Restatement of Contracts.
Step-by-step explanation:
The resource that is not "the law", but is a codification of what the ALI regards as the best rulings of contract law and which is used by judges as a reference in deciding contracts cases is the Restatement of Contracts. The Restatement of Contracts is a publication by the American Law Institute (ALI) that summarizes and organizes the principles of contract law as developed by courts in the United States. It provides a valuable guide for judges in interpreting and applying contract laws.