WASHINGTON (Reuters) -Labor unions filed a lawsuit against the U.S. government on Thursday, alleging that the Trump administration violated the First Amendment rights of people who are legally in the United States by searching their social media for specific viewpoints, including criticism of Israel.

The complaint is the latest legal challenge to the broad immigration crackdown initiated since President Donald Trump was inaugurated in January, which has seen unprecedented deportations of migrants, including some who had valid visas.

The Department of State on Tuesday said it had revoked the visas of at least six people over social media comments made about the assassination of conservative activist Charlie Kirk. 

Three major trade unions -- United Auto Workers, Communications Workers of America and American Federation of Teachers -- sued the State Department, the Department of Homeland Security, the U.S. Citizenship and Immigration Service, Immigration and Customs Enforcement and the heads of these agencies at a federal court in New York.

Responding to a request for comment, State Department Principal Deputy Spokesperson Tommy Pigott said: "The United States is under no obligation to allow foreign aliens to come to our country, commit acts of anti-American, pro-terrorist, and antisemitic hate, or incite violence. We will continue to revoke the visas of those who put the safety of our citizens at risk."

Trump officials have argued that foreigners do not have the same constitutional rights as U.S. citizens and that a visa is a privilege not a right.

The complaint by the labor unions cites high-profile cases and the comments of officials themselves to argue that a government program uses artificial intelligence and other automated tools to monitor visa holders' posts and singles out individuals with negative views toward the U.S. government and the Trump administration in particular, U.S. culture and what the government deems "hateful ideology."

The federal government has broadly defined support for terrorism to include criticism of U.S. support for Israel, of Israel's actions and support of Palestinians and used this as a reason to cancel visas, they said. The complaint cited cases including green card holder Mahmoud Khalil, who was released in June following months in detention after the administration sought to deport him for taking part in pro-Palestinian protests.

The unions argue this has chilled the speech of thousands of their members by threatening immigration action if the government disapproves of their views.

Many union members have stopped expressing their views because "the government has promised and proven that saying the wrong thing can trigger life-altering immigration consequences, particularly for visa holders and Lawful Permanent Residents," the complaint says.