xp_revokelogin (Transact-SQL)
Applies to: 
SQL Server
Revokes access from a Windows group or user to SQL Server.
Important
This feature will be removed in a future version of SQL Server. Avoid using this feature in new development work, and plan to modify applications that currently use this feature. Use DROP LOGIN instead.
Transact-SQL syntax conventions
Syntax
xp_revokelogin { [ @loginame = ] 'login' }
Arguments
[ @loginame = ] 'login'
The name of the Windows user or group from which to revoke access. @loginame must include the domain name, for example [CONTOSO\sylvester1]. @loginame is sysname, with no default.
Return code values
0 (success) or 1 (failure).
Remarks
Use DROP LOGIN instead.
Permissions
Requires ALTER ANY LOGIN permission on the server.