Your bags (and your person) are subject to search without consent. It is not like a TSA checkpoint because the purpose of the search is limited to ensuring that duty is paid is imported items that require it, and that no contraband is imported. There are specific laws that require the payment of duty and that prohibit contraband and the limited administrative search is authorized as an exception to the 4th Amendment to enforce them. That is very different from the TSA checkpoint search, because there are no laws that require a person not possess WEI within the U.S. In the event of a poorly designed TSA checkpoint (or airport), the correct way to handle it is as was related in the link in an earlier post, i.e. the passenger who refuses the TSA search can be escorted to the non-sterile area of the airport. The alternative, i.e. compelling a security search, is both violative of the law and offensive to the Constitution.