That'll have been target driven policing: pressure to announce X number of drug busts in order to justify the budget spent.
I strongly suspect this is Operation Something-Or-Other too, given Scotchland's position on air guns. The distinction between airsoft and air guns isn't going to much bother a copper who's been told to go and find X examples of Scotchmen posing with shooters.
That said, in my younger days I was both illegally searched by ScotPlod and giving a casual slapping in the back of a van, so I'm not going to leap to their defence. Recently, a colleague collared a ned who was setting fire to his garage, dragged him inside, called ScotPlod, and they turned up, arrested him, and offered him a caution for unlawful detention. He (correctly) told them to do one, the Fiscal harpies took it to court, and fortunately the Sheriff sent them away with a bee in their ear. He's currently going down the route of suing ScotPlod for unlawful arrest (Tommika nailed that it's down to whether it was necessary at the time, not based on the final result of the case).
Sad, but not shocking - it's far easier for the Criminals' Justice System to target the generally law abiding, and it wouldn't surprise me to hear that the chap in this case was offered a caution too, just to hit their sanctioned-detection targets, and turned it down.
