President Joe Biden on Tuesday signed an executive order to restrict asylum seekers at the U.S.-Mexico border, using a controversial regulation last introduced by his predecessor.

The new restriction will effectively halt the number of migrants able to cross into the U.S. once a daily cap has been reached and allow officials to swiftly deport those who enter illegally.

The measure would kick in once illegal entries surpassed 2,500 per day over a seven-day average, which means it would take effect immediately as crossings already surpass that figure.

Legal challenges are expected, with the American Civil Liberties Union (ACLU) telling Newsweek on Tuesday that it would be reading the order closely.

Following the White House announcement, the ACLU confirmed it would sue, just as it had during the Trump administration.