Per public announcement from TSA.Gov, the persons refusing to show ID will be denied access to the sterile area. http://www.tsa.gov/press/happenings/...uirements.shtm

It states that this is covered under the authority granted by 49 C.F.R. § 1540.105(a)(2). I do not have the specific passage, but you can access the above listed reg via online at
http://law.justia.com/us/cfr/title49....8.2.10.3.html

Hope this answers the question for you.