Old news that I didn't know: You can opt out of the backscatter machine, but you can NOT opt out of finishing the security screening (i.e., the patdown), once you've put any luggage on the belt. So says the Supreme Court: http://www.wired.com/threatlevel/2007/08/court-says-trav/
I'm not from the US, so maybe I'm misunderstanding your legal system, but that appears to be a ruling by an appeals court, not the Supreme Court. It also appears to predate the current security checks, where the alternatives of being virtually strip searched or sexually assaulted are each dubious on both ethical and, at least under other circumstances, legal grounds. It seems to me as a non-lawyer that such a ruling might be challenged on several grounds today, not least constitutional ones.
It's a ruling by the 9th Circuit Court, a step below the Supreme Court. The appellate courts have regional jurisdiction. As it happens, San Diego, where this incident occurred, is in the 9th Circuit, so this ruling would be the law unless or until it is overturned by the Supreme Court.
