While the CTA has, for most of its history, involved an open or relatively open border, since the Second World War this has not meant that someone who legally entered one part of the CTA was automatically entitled to enter another part. Unlike the Schengen Agreement, the CTA currently provides no mechanism for the mutual recognition of leave to enter and remain, and the UK and Ireland operate separate visa systems with distinct entry requirements. In general, a British visa will not allow entry to Ireland nor vice versa.