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 UK visa will not allow entry to Ireland nor vice versa.
The Channel Islands and the Isle of Man allow entry to holders of UK visas (with some exceptions). Bailiwick of Guernsey and Jersey immigration authorities routinely check non-EEA nationals seeking to enter the UK to ensure they have valid UK permissions.
In July 2011 Ireland introduced a limited pilot visa waiver programme under which the normal requirement for certain nationalities to hold an Irish visa is waived for visitors to the UK who hold valid UK visas.
Nationalities that are visa-free in the UK but not in Ireland
Nationalities that are visa-free in Ireland but not in the UK
Irish visa-waiver nationalities