Staff and visitors to the headquarters of North Wales Police in Colwyn Bay have come under attack from an angry seagull.
A spokeswoman said the bird was protecting its nest
Officials said the swooping bird was a health and safety issue, and removed the bird's nest from the building.
A spokeswoman said the destruction of the nest was done lawfully. Since its removal, the seagull has disappeared.
But staff have been warned that if it returns, they must not take the "law into their own hands".
A spokeswoman said gulls were naturally protective when nesting, and that the bird was attacking people who approached the front door.
A wildlife officer sent an email to all staff at Colwyn Bay, warning them not to take the law into their own hands if there are further problems with herring gulls.
The email reminded staff of the legal protection given to herring gulls.
It said any action taken against the birds must be lawful, and be requested by the building manager.