Dhaka, 27 June, Abnews: Seventeen US states have sued the Trump administration over its "cruel and unlawful" break-up of migrant families.
Democratic attorneys general from states including Washington, New York and California launched the lawsuit.
The legal action objects to the policy of refusing entry to asylum seekers at the US-Mexico border.
Meanwhile, a California judge has ruled that all families of undocumented immigrants separated at the US border must be reunited within 30 days.
San Diego judge Dana Sabraw also said that children under the age of five must be back with their parents within 14 days as he granted the American Civil Liberties Union (ACLU) a preliminary injunction in a lawsuit filed over the family separations.
Court papers filed by the ACLU on Monday contained numerous accounts of parents unable to locate or communicate with their children after they were separated by border officials.
On Tuesday, Massachusetts, Delaware, Iowa, Illinois, Maryland, Minnesota, New Jersey, New Mexico, North Carolina, Oregon, Pennsylvania, Rhode Island, Vermont and Virginia plus the District of Columbia were the other states suing President Donald Trump's administration.
In legal action filed with the US District Court in Seattle, Washington, Mr Trump's 20 June order to keep migrant families together was also described as "illusory".
It is the first legal challenge over family separation from the states, which argue that the Republican president's executive order denies migrant families due process and the right to seek asylum.
Speaking at a news conference in Brazil on Tuesday, US Vice-President Mike Pence warned undocumented immigrants not to "risk the lives of your children" by trying to enter the US illegally.
He said he had a message "straight from my heart" for those planning a journey to America: "If you can't come legally, don't come at all."
"Don't risk your lives or the lives of your children by trying to come to the United States on a road run by drug smugglers and human traffickers," Mr Pence added.
Last week, Mr Trump called for speedy deportations, just days after he issued the executive order.
States are now seeking a court order to reunite families and end the separation practice by declaring it "contrary to the Constitution".
Tuesday's lawsuit states that Mr Trump's order does not mandate the end of family separation and says nothing about reuniting families who have already been separated.
It also calls the policy "an affront" to the states' interests in maintaining standards of care for children and preserving parent-child relationships.
"The policy, and the administration's related conduct, has caused severe and immediate harm to the States and their residents."
New Jersey Attorney General Gurbir Grewal said in a statement that the practice of separating families "is cruel, plain and simple", the Associated Press reported.
"Every day, it seems like the administration is issuing new, contradictory policies and relying on new, contradictory justifications. But we can't forget - the lives of real people hang in the balance."