a karate expert

A man walked into a bar, drank a few beers and started to walk out without paying. The barman saw him and called: "Hey, what about paying for your drinks?"

"Watch it," the man said. "I'm a karate expert." The barman decided to let him walk out, but advised the pub owner to hire two bouncers, both karate experts themselves.

The next time the man started to leave without paying, the bouncers approached him. "Watch out!", he warned. "I'm a karate expert."

"So are we," the bouncers said.

"Well you are lucky," said the man. "The drinks here are free!"