When do you get an 'Access Denied by Access Control List' error message?

An access control list is a list that specifies the permissions for reading, writing, and executing a particular file, folder, or a program. This access control list has access control entries which specify the users, their roles, and the permissions, as a string of bits called access masks.

These permissions and the list are created by the administrator of the system. If the administrator does not give proper permission for a particular user to use a program, then if the user tries to use that program he might get the ‘Access Denied by Access Control List’ error.

Some of the scenario that might trigger this error is when a user tries to connect to the internet through a particular ISP, where he is not having the permission to connect to that ISP. The administrator might not have given access to that particular user to connect to that particular ISP.