Macke Co. v. Pizza of Gaithersburg, Inc. 259 Md. 479, 270 A.2d 645 (Md. 1970) Gaithersburg had contracted with Virginia Coffee Service to provide their restaurants with beverage machines for five years.  A year later, Virginia was bought out by Macke. Gaithersburg canceled the contract.  Macke sued. The Trial Court found for Gaithersburg, Macke appealed. The Trial Court found that Virginia's reputation was a key reason Gaithersburg contracted with them.  Macke did not have that reputation, so the contract had fundamentally changed. Gaithersburg had considered Macke for the initial contract, but chose to contract with Virginia instead. The Court also found that damages could not be estimated since this was a requirements contract. The Appellate Court reversed and remanded for trial. The Appellate Court found that in the absence of a contrary provision, rights and duties under and executory bilateral contract may be assigned and delegated, with two exceptions: Contracts to provide personal services. Contracts where delectus personae is an element. Literally "choice of partners". The case was remanded for trial to determine damages. In order for Gaithersburg to prevail, they would need to show that there is a material difference in the contract.  It's a very objective test. Compare to Fursmidt v. Hotel Abbey Holding Corp., which talks about objective vs. subjective standards. You can theoretically put a provision into a contract saying that the rights are not assignable.  But it's generally not a good idea to sign away that right, so it's pretty rare.