Immigration and Customs Enforcement agents are expected to round up thousands of undocumented immigrants for deportation starting this weekend.
The nationwide raids are expected to take place in at least 10 major cities, including New York.
Administration officials say ICE agents are targeting at least 2,000 immigrants who either missed their court dates or ignored deportation orders.
Many of those immigrants were given notice to report to an ICE office and leave the U.S. in February.
The operation, backed by President Donald Trump, had been postponed earlier this month, due to resistance among officials at his own immigration agency.
An ICE spokesman said in a statement that the agency would not comment on specific details of the operations to ensure the safety and security of agency personnel.
The American Civil Liberties Union, or ACLU, filed a preemptive lawsuit Thursday in order to protect refugee families and children, many of whom have fled violence in their own country. The suit argues that constitutional due process requires the government to bring them before an immigration judge so they can have a fair day in court before they face deportation.