The man was enjoying a day out at the recent Gothenburg Cultural Festival when two plainclothes police officers approached a woman nearby who was openly smoking a joint.
In a panic, the man threw away his bag of cannabis but was spotted by the officers who then made a beeline for the hapless stoner.
It was at this point a gull dived down from the skies above, snatching the drugs and flying away.
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Police spokesman Stefan Gustafsson said that as the officers watched the bird fly away with the evidence, the lucky man fled the scene.
"The policemen stood and watched the evidence disappear into the sky," said Gustafsson.
Another police spokeswoman, Camilla Fogelhamre, told Expressen that "I've heard a lot during the years I've worked in the police, but never anything like this".
"We did not spend any major resources on finding the right seagull. It was a little difficult to follow and we did not deploy a helicopter."
The woman smoking the joint did not fare so well, with officers arresting her in what police described as "a patch over the wound".
While all animal species process intoxicants differently, no peer-reviewed studies have been completed into the effects of THC on birds.
Studies have shown, however, that birds are much more susceptible to toxins in smoke due to their bodies having very efficient respiratory systems which extract much more air particulates than humans.