FYI, only local "Administrators" and "Remote Desktop Users" group users can login via "Remote Desktop". Just use MMC to add the users to the "Remote Desktop Users" group of corresponding workstations.
You can also configure more groups with GPO.
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Alternatively, you can also set "Log On To" settings on those users with "Active Directory Users and Computers" MMC addin. This will restrict the account to only be able to login the selected computer.