Forget about the dragons

It is illegal to slay a dragon. Even in self-defense.
Sure, there are no dragons in England anymore, but the law is the law, and it’s still illegal to slay dragons.
So when HM Revenue saw “Dragonslayer” on my return, I was picked up for questioning.
“Don’t you know that it’s illegal to slay dragons?” said the agent.
“There aren’t any dragons anymore,” I said. “There’s none left to slay.”
At that point, they handcuffed me and read me my rights.
“Why are you arresting me?” I said.
“You just couldn’t stop, could you?” they said. “You killed them all!”