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Join Date: Sep 2002
Location: LAX/TPE
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Posts: 42,331
Since only real law enforcement can detain you, absent their presence, there is nothing to stop you from flipping off the screeners, grabbing your stuff and walking out - they have no legal authority to stop or physically detain you.
Until the police show up (which might not happen in time if you move quickly), you're pretty much in the clear. If the police do catch up with you after the fact, you can just say you refused to be physically accosted by the screener and wanted to leave.