(NewsNation) — Nearly one week has passed since President Joe Biden took executive action targeting illegal border crossings.

The action implemented stricter policies on asylum-seekers if the daily average of illegal crossings exceeds 2,500. However, averages at the southern border haven’t been below that threshold in years.

Biden claims Republicans left him no choice, while former President Donald Trump dismissed it as a meaningless public relations ploy.

More migrants in custody after border action

U.S. Customs and Border Protection (CBP) data shows that the executive action hasn’t greatly impacted the number of illegal crossings.

There were more than 3,500 encounters along the southern border in the three days before the executive action took effect, according to data provided to NewsNation by CBP sources.

Starting last Wednesday, the first full day after Biden’s announcement, there was no significant change in the number of border encounters; Border Patrol agents apprehended about 4,000 migrants trying to illegally cross the border. Although encounters dipped slightly Friday, the number of migrants in custody spiked to more than 10,000 on Saturday.

ACLU plans to challenge action

The American Civil Liberties Union (ACLU) plans to challenge the executive action in court, arguing it illegally restricts the right to seek asylum.

“We need solutions to address the challenges at the border, but the administration’s planned executive actions will put thousands of lives at risk,” Deirdre Schifeling, the ACLU’s chief political and advocacy officer, said in a statement.

Texas Gov. Greg Abbott expressed concerns in an interview on Fox News’ “Sunday Morning Futures,” suggesting that the executive action will only encourage more illegal crossings.

“All that this new Biden policy is going to do is to actually attract and invite even more people to cross the border illegally,” Abbott said.

Meanwhile, Homeland Security Secretary Alejandro Mayorkas defended Biden’s plan, stating it’ll change the risk calculus for migrants and encourage them to find a lawful pathway to the U.S.

Concerns over the cost of deporting migrants

Enforcing the new executive action will incur significant costs.

There are questions and concerns about how the Biden administration and border agents will deport migrants found crossing illegally without additional funding.

According to data from CBP sources, thousands of migrants from countries such as China, India, Brazil and Peru tried to cross the southern border illegally last month.