The raids targeted more than 100 people - mostly Chaldean Christians, but also Shiite Muslims and Christian converts, advocates said.
Most have lived in the US for decades and fear being targeted by extremists should they be sent back to Iraq.
US Immigration and Customs Enforcement said the immigrants targeted in the weekend raids all had criminal records.
Seven of the detainees participated in the class action lawsuit asking a federal court in Michigan to halt the deportation process for all of those arrested.
"Not only is it immoral to send people to a country where they are likely to be violently persecuted, it expressly violates United States and international law and treaties," said Kary Moss, head of the Michigan chapter of the American Civil Liberties Union, which filed the suit on the detainees' behalf.
The weekend raids sent chills through the sizeable community of Chaldean Christians in the Detroit area, who comprised the majority of those arrested.
"We have seen a number of families who are completely shaken up, in particular kids who are missing a parent," Nathan Kalasho, a Chaldean Christian who operates a charter school in the Detroit area, told AFP prior to the lawsuit being filed.
'Inhumane'
The Christian population in Iraq has shrunk dramatically, and Kalasho said Iraqi immigrants in Detroit do not believe the Middle Eastern country is safe for religious minorities.
"To send these folks back to a war zone is inhumane," he said.
A felony conviction is grounds for deportation in the US, but until a March deal between the two countries, Iraq had not had a policy of accepting its repatriated citizens from the US.
The ACLU countered in its court filing that many of the detainees had minor offenses, and committed no additional crimes after their convictions.
The group is requesting a hearing Friday at the US District court in Detroit, to ask for a temporary stay to pause impending deportations.
