The Schengen Agreement is a treaty between European states that abolished systematic border controls between participating countries. It was first signed in 1985 in the town of Schengen, Luxembourg. As of 2007, 24 states and Monaco had abolished border controls on persons among themselves, allowing for unlimited freedom of movement between member states. While advantages include faster travel and movement between borders, disadvantages include more stringent controls on external borders and potential issues with illegal movement across internal borders. Several additional countries are candidates to join the Schengen Area in the future as EU membership is obtained.