How to inactivate / release a resource from project and time sheet entry against the project?

Hi,

Although we have reassigned a project team member to make him inactive as a project resource but the team member is still able to create his timesheets against the project and activities that he was earlier assigned.

We would like to know how to inactivate or release the resource from the project completely so that he can't enter his timesheets against the project or activities in future.

Kindly help.

Thanks,
Himansu