I am advised by the Irish Naturalisation & Immigration Service (INIS) of my Department that an immigration officer may under Section 4 of the Immigration Act, 2004 refuse to give permission to enter the State under certain circumstances. It is important to note that a Visa is a pre-clearance to present at the port of entry only and carries no automatic right of entry into the State. The actual permission to enter the State is given by the Immigration Officer at the port of entry, who has discretion whether to grant entry. This includes where an immigration officer has reason to believe that the non-national's entry into, or presence, in the State could pose a threat to national security, or can be contrary to public policy, and where there is reason to believe that a non-national intends to enter for purposes other than that expressed by him/her.
Additional checks are carried out as required with An Garda Síochána and other countries' immigration and police authorities as part of the visa application process for visa required nationals. Checks are also carried out with the United Kingdom authorities in the context of maintaining the integrity of the Common Travel Area. Finally, visa required nationals must declare in their visa application if they have any criminal convictions in any country.