Oh, for crying out loud....
Use your head. What most basic of Constitutional rights is being trod upon when a policeman asks to look in my briefcase? It happens at stadiums, it happens at courthouses, it happens in airports.
Adults need to stop being such whiney babies. We're setting a bad example for the children.
Amendment IV
The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no warrants shall issue, but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.
None at all, if all he does is ask. Then you can say "No" and go on about your business. If you can't say "No" and go on about your business, then your right to be secure in your person and your effects has just been shot in the head.