The United States Department of Homeland Security said on Saturday that foreign nationals who have stayed in the country for 30 days or more (as of April 11) must register with the country’s Citizenship and Immigration Services or face arrest and deportation.

Foreigners with valid visas – such as H-1B visa holders, Green Card holders and international students – will be considered registered and should not be impacted by the move, but will be required to carry documentation with them at all times, The Times of India reported quoting unidentified immigration lawyers.

AP reported that the directive applies only to foreigners staying in the US illegally.

According to the Trump administration, between 2.2 million and 3.2 million persons could be affected by the move. Minors who turn 14 in the US have been told to “re-register and submit fingerprints within 30 days of your 14th birthday, even if previously registered”.

“President Trump and I have a clear message for those in our country illegally: leave now,” said Secretary of Homeland Security Kristi Noem. “If you leave now, you may have the opportunity to return and enjoy our freedom and live the American dream.”

White House Press Secretary Karoline Leavitt stated that all those who do not comply “will be arrested, fined, deported, never to return to our country again”.

A US federal judge on Thursday allowed President Donald Trump’s administration to enforce this requirement starting Friday, AP reported.

The US has long required non-citizens, including undocumented immigrants, to register with the government as per the 1940 Alien Registration Act and the 1952 Immigration and Nationality Act, according to AP. However, the move was rarely enforced.

The last time such a requirement was imposed was after the terrorist attacks of September 11, 2001. The authorities required male non-citizens from 25 countries to register under a program that led to over 13,000 deportation cases but no terrorism convictions. The program ended in 2016.

The Trump administration maintained that the registration requirement had always been in place and that it was merely ensuring its widespread and equal enforcement.

These measures are part of a wider crackdown by the Trump administration on undocumented migrants that includes mass deportations.

Six hundred and thirty-six Indians have been deported from the United States since January, when the Donald Trump administration assumed office, the Union government has told Parliament.

Three hundred and forty-one were deported to India by chartered flights while many others were repatriated on US military aircraft. Two hundred and forty arrived on commercial flights and 55 on separate commercial flights through Panama.

Reports in January said that India was working with the Trump administration to deport around 18,000 undocumented or visa-overstaying Indian citizens from the US.