TSA has no constitutional authority to serch you or your belongings. Granted if you refuse the search you can't board the carrier. TSA is chock full of nit wits and they should be disbanded. Airports should go with private screeners. TSA has not caught one terrorist to date.
Customs, now that's a different story. CBP has constitutional authority to search you and your property and unlike deciding not to fly once you've presented yourself for inspection the game is on, no backing out.