I would gladly wish sharks away. But that won't make them go away, nor the laws that they seek to enforce.
If the terrorist tries to overpower me and is intent on sacrificing the aircraft and all of it's passengers, I'll gladly accept any liability for shooting the bastard.
Trouble is, we still don't KNOW whether the hijacker is intent on wrecking the craft. The hijackers in Sept 11 lied and promised to land the craft safely.
No, if there is going to be a do-it-yourself firefight aboard an aircraft (probably just the passenger if the security system is worth a hoot, as it did screen out guns on Sept 11) the passenger had darn well be sure that the hijacker really means to crash the craft as the risk of breaching the hull is too great. That task I gladly and unashamedly would rather see assigned to sky marshals or at MOST passengers SPECIALLY licensed, trained, and tested. As for on the ground, I am with you as that there should be no gun restrictions whatsoever except for the insane or contemporary with punishment for a crime.
From now on, we must assume that every hijacker is a suicide bomber. Should we or the authorities err in some case, the onus is on the hijacker. The suicide bombers have forever changed the rules of engagement.