Abstract: A method, system and computer program product for selectively restricting access to a program function in a computer system having an operating system security mechanism operates via an application programming interface (API) that includes a program function registration API function, an authorization selection API function, and an authorization query API function. In response to a call to the API registration function, the program function is registered in a repository in the computer system. After the program function has been registered, a system administrator can select user authorizations using a software tool that includes calls to the authorization selection API function. The system administrator may select whether a particular user or group of users is authorized to access each registered program function. A programmer can embed a call to the authorization query API function in an application program, which includes or calls the program function.