And one of them who is not being granted a waiver is desperate to get to Missouri where his sister is suffering from terminal cancer.
Kevin O'Brien, who lives in Tuam, County Galway, has been to the U.S. on several occasions. He served time in the H-Blocks during the Troubles but subsequent to his release was able to enter the U.S.
He attempted another visit a few years ago but was stopped at Shannon by U.S. immigration officers. His wife and two children were allowed to proceed.
O'Brien applied by email for a visa from the U.S. Embassy in Dublin in May of last year and was told he would get a response by email in a couple of weeks.
He did not. He later went to the embassy for an interview but has heard nothing following this either. The reason for the visa denial remains a mystery to O'Brien and his family who have enlisted the aid of U.S. Senator for Missouri, Claire McCaskill, and the New York law firm of O'Dwyer and Bernstien.
McCaskill has been in contact with the family and her office is working on the case.
Attorney Brian O'Dwyer points to the fact that O'Brien has not been allowed enter the U.S. since 9/11, but this has not been presented as a factor in the case to O'Brien or his family.
"There is no known impediment. It's a mystery," said O'Dwyer.
O'Brien has a number of relatives living in Missouri, mainly in the St. Louis area. They include three sisters and a brother.
In what is a familiar position for many undocumented Irish who cannot return to Ireland for even the most important family matters, O'Brien is unable to be at the side of his sister, Pauline, when it most counts.
He also missed a family wedding in Missouri last year due to his lack of permission to travel.