There is no other way. A user's groups are checked at logon and there for the security setting are issued to the user through group membership.
A logoff and logon might get you some annoyed users but afaik it's the only way. Whether or not it's a forced logoff depends on the changes you made and how sensitive the data is that the user should no longer access.
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Mart

- Chuck Norris once sold ebay to ebay on ebay.