Lawyers for the American Civil Liberties Union raced Friday evening to stop the Trump administration from deporting a new group of Venezuelan migrants accused of being gang members under the expansive powers of a rarely invoked wartime law.

More than 50 Venezuelans were scheduled to be flown out of the country — presumably to El Salvador — from an immigration detention center in Anson, Texas, according to two people with knowledge of the situation. The ACLU in recent days has secured court orders barring similar deportations under the law, the Alien Enemies Act, in places including New York, Denver and Brownsville, Texas.

The situation in Anson was urgent enough that ACLU lawyers pressed their case in three different courts within five hours.

The lawyers started with an emergency filing in U.S. District Court in Abilene, Texas, in which they claimed that officers at the Bluebonnet Detention Center in Anson had started distributing notices to Venezuelan immigrants informing them that they could face deportation as soon as Friday night.

They asked Judge James Wesley Hendrix, who is overseeing the case, to issue an immediate order protecting all migrants in the Northern District of Texas who might face deportation under the Alien Enemies Act. When Hendrix did not grant their request quickly, the lawyers filed a similar request to the U.S. Court of Appeals for the 5th Circuit in New Orleans.

The lawyers then filed an emergency petition to the Supreme Court, asking the justices to step in and issue an immediate pause on any deportations because many of the Venezuelan men had “already been loaded on to buses, presumably headed to the airport.”

Immigration lawyers have been playing a high-stakes game of cat and mouse with the federal government since President Donald Trump issued a proclamation last month invoking the Alien Enemies Act as a way to deport immigrants he claims are members of Tren de Aragua, a violent Venezuelan street gang. The law, which was passed in 1798, has been used only three times before in U.S. history, during periods of declared war.

The efforts by groups like the ACLU to stop deportations under the act were complicated this month by a Supreme Court ruling that found that anyone subject to the statute needed to be given the opportunity to challenge their removal, but only in the places where they were being detained.

The decision by the justices set off a hunt for anyone who might fall under the authority of Trump’s proclamation. The ACLU, hoping to come up with a system for determining where those people might be, has asked a federal judge in Washington to issue a nationwide order forcing the administration to provide 30 days’ notice to anyone in the country before officials seek to remove them under the act.

The Washington judge, James E. Boasberg, has set a hearing for Monday to discuss the request. In the meantime, the lawyers have to rely on a whisper network to figure out who to file cases on behalf of and where to file them.