A bailiff is an officer of the court. A bailiff has duties such as making arrests and maintaining order in court.
This legal officer has a different job depending on the country: in the US, a bailiff is a kind of court usher and security guard. In the UK, bailiffs carry out writs and execute repossession orders. In all cases, the bailiff serves a higher authority: the court. This may be because the word was first used for officers of the king, including sheriffs and mayors. As democratic authorities replaced monarchies, the concept of the bailiff evolved.