Why the users are still able to checkout the same file even it's been disabled?

In visual studio, team explorer> project settings> source control I have disabled the Multiple Check-outs and also enforced check-in policy for a project. Also, I have changed the workspace to server version but still, the programmers of the projects are able to checkout at a time. why?

Solution

Please change your location of your workspace to server. Here are the steps:

1.Team->Team Project Collection Settings->Source Control...->Workspace Settings Tab

Change the default workspace type from "Local (recommended)" to "Server". 2.Source Control Explorer->Workspace Combobox->Workspaces...->Edit...->Advanced->Location Please let other users change the location from "Local" to "Server".