How it could Work.[]
For projectile weaponry, it would not be that hard to disable regular guns.
Options for energy weapon-The Tollan W.D could have depleted the naquadah cells, but that seems unlikely to me...or it could just "jam" the weapon somehow, perhaps by cutting of the flow of power to the emitters in the end of the Staff or Zat. Or, the Tollan could have had transporter tech, and the W.D removed the liquid naquadah cells and the jammed Tau'ri guns by realigning the molecular structure of the barrel or warping the copper casing of the bullets. Just some thoughts.