CREATE TRIGGER Restrict_SSMS_For_Other_Users
ON ALL SERVER 
FOR LOGON
AS
BEGIN
IF SUSER_NAME() <> 'MyDomain\PrivilegedUser'  AND EXISTS (SELECT *
   FROM sys.dm_exec_sessions
   WHERE session_id = @@SPID
   AND program_name IN (N'Microsoft SQL Server Management Studio - Query')
    ROLLBACK;
END;