US President Donald Trump on Friday denied signing a proclamation invoking a 200-year-old law to deport alleged Venezuelan gang members who were sent to prison in El Salvador.

His downplaying of his role in the affair came just hours after a federal judge called Trump?s use of the law ?incredibly troublesome.?

Last weekend Trump invoked the rare wartime Alien Enemies Act to deport 238 men his administration alleged were members of the Venezuelan gang Tren de Aragua and send them to a maximum security prison in El Salvador.

In a statement at the time, the White House press secretary wrote that Trump ?signed a Proclamation Invoking the Alien Enemies Act? and the document additionally appears in the Federal Register with Trump?s signature on it.

But on Friday, Trump suggested his secretary of state had more to do with the matter, telling reporters: ?I don?t know when it was signed because I didn?t sign it. Other people handled it.?

?Marco Rubio has done a great job and he wanted them out and we go along with that,? Trump said.

Earlier in the day a federal judge said that Trump?s use of the little-known law to deport the alleged gang members was ?incredibly troublesome.?

At a hearing on Friday, James Boasberg, the chief judge of the US District Court in Washington, questioned the legality of using the 1798 Alien Enemies Act (AEA) to summarily send the Venezuelan migrants to the prison in El Salvador.

?The policy ramifications of this are incredibly troublesome and problematic and concerning,? Boasberg said.

He noted that the only previous uses of the AEA were ?in the War of 1812, World War I and World War II, when there was no question there was a declaration of war and who the enemy was.?

? Troublemaker and agitator ?

Last weekend Boasberg issued an emergency order against deportation of the Venezuelans and said two flights already in the ar needed to turn around.

The Justice Department has claimed the planes were in international airspace when the judge issued his written order directing them to return and his jurisdiction no longer applied.

The episode earned Trump?s ire and the Republican president called on Tuesday for Boasberg?s impeachment, branding the judge a ?troublemaker and agitator.?

Those remarks by Trump drew a rare public rebuke from Supreme Court Chief Justice John Roberts who said ?impeachment is not an appropriate response to disagreement concerning a judicial decision.?

Lee Gelernt, a lawyer for the American Civil Liberties Union, which filed suit against the deportations along with other rights groups, noted that even during World War II ?people got hearings.?

?It was not this summary removal,? Gelernt said.

?You have to be able to contest,? he said. ?Otherwise anyone could be taken off the street.?

Attorneys for several of the deported Venezuelans have said their clients were not members of the Tren de Aragua gang, had committed no crimes and were targeted only because of their tattoos.

Boasberg meanwhile said at Friday?s hearing that ?the government?s not being terribly cooperative at this point but I will get to the bottom of whether they violated my order.?

? ?A bad group? ?

Speaking to reporters in the Oval Office on Friday before denying signing the proclamation, Trump defended the deportations under the AEA, which was last used during World War II to intern Japanese residents.

?I was told that they went through a very strong vetting process,? Trump said. ?This was a bad group? killers, murderers and people that were really bad with the worst records you?ve ever seen.?

The New York Times reported meanwhile that nearly the entire civil rights branch of the Department of Homeland Security was fired on Friday.

The department?s Office for Civil Rights and Civil Liberties was responsible for oversight of the administration?s efforts to crack down on illegal immigration. (AFP)

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