To undo any Thirdwall policy, open the Thirdwall Location screen where the policy is enabled and browse to the policy that you want undone. All enabled Thirdwall policies will have an "UNDO" link.

Clicking the "UNDO" link will produce the following dialog box:

From the UNDo dialog you can either permanently Undo and remove the policy, or create a "Temporary" exception for the policy for an allotted amount if time.