The debate over expanded screening touches on the proper balance between safety and civil liberties. Some legal experts wonder whether the TSA violates the Fourth Amendment protection against unreasonable search and seizure. Mr. Pistole is bracing for a grilling on Capitol Hill and likely legal challenges. But some critics, such as the former head of American Airlines Robert Crandall, question the TSA’s methods from a security point of view. The agency treats each and every passenger as an equal terrorist threat. As a result, the vast majority of resources are devoted to where little threat exists.