Cork man Keith Byrne has been told he must leave the US by Friday or spend time in jail, according to his family.
They say if he doesn't sign a document agreeing to leave and not apply to return for five years he'll be remanded to a federal prison as he waits to appeal his case.
The 37-year-old was arrested by Immigration and Customs Enforcement (ICE) a week ago in Pennysylvania, where he lives with his wife Keren and three children.
He runs his own painting company in the States.
Keith went to the US in 2007 under the visa waiver programme and overstayed.
Following his arrest, he's being held at a detention facility in Scranton, Pennsylvania
He has two marijuana possession charges dating from his early 20s while in Ireland, and his family says Mr Byrne 'readily admitted' to that when he applied for US citizenship.
If he stays in the US and his appeal fails, he could ultimately face up to five years in jail.
Keith's father Jim says the family doesn't know what to do next.
He explained: "It's very hard in these circumstances to be making decisions on your future.
"It's up to the powers that be over there... I don't know which way it's going to swing.
"I just hope they come down on humanitarian grounds to keep a family [that's] going to be split down the middle together."
Mr Byrne said if his son signs the form he'd be given a passport, sent home within three weeks and wouldn't be able to apply to return to the US for five years.
He added: "If he didn't sign, he'd be sent to the state penitentiary - where he'd be waiting at least a year to see a federal judge.
"If he failed with the judge, he could spend up to four to five years in a federal penitentiary."
