A system regulates access to resources requested by an operation executing on a computer. The operation invokes a plurality of methods that operate upon code during execution. The system includes a policy file, a call stack, and an execution unit. The policy file stores permissions for each of the resources. The permissions authorize particular types of access to the resource based on a source of the code and an executor of the code. The call stack stores representations of the methods and executors in an order of invocation by the operation. The execution unit grants access to the resource when the types of access authorized by the permissions of all of the methods and executors on the call stack encompass the access requested by the operation.