President Donald Trump's administration has said it will assess applicants for US work, study and immigration visas for "anti-Americanism" and count any such finding against them.
The US Citizenship and Immigration Services said in a "policy alert" that it gave immigration officers new guidance on how to exercise discretion in cases where foreign applicants "support or promote anti-American ideologies or activities" as well as "antisemitic terrorism."
Trump has labelled a range of voices as anti-American, including historians and museums documenting US slavery and pro-Palestinian protesters opposing US ally Israel's military assault on Gaza.
"Anti-American activity will be an overwhelmingly negative factor in any discretionary analysis," USCIS said.
"America's benefits should not be given to those who despise the country and promote anti-American ideologies."
The announcement did not define anti-Americanism. But the policy manual refers to a section of federal law about prohibiting naturalisation of people "opposed to government or law, or who favour totalitarian forms of government."
Aaron Reichlin-Melnick, a senior fellow at the American Immigration Council, said the step had echoes of the 1950s when Senator Joseph McCarthy hunted alleged communists in a campaign that became synonymous with political persecution.
"McCarthyism returns to immigration law," he said. Anti-Americanism "has no prior precedent in immigration law and its definition is entirely up to the Trump admin."
Meanwhile a federal appeals court has cleared the way for the Trump administration to end temporary deportation protections and cancel work permits for more than 60,000 immigrants from Central America and Nepal.
The ruling by the US Court of Appeals for the Ninth Circuit allows the government to end Temporary Protected Status for immigrants from Nicaragua, Honduras and Nepal while a court challenge to that policy plays out.
The order immediately ends protections for Nepalis, which expired on August 5. Protections for Hondurans and Nicaraguans will expire on September 8.
US Department of Homeland Security spokeswoman Tricia McLaughlin said the decision will help restore integrity to the immigration system and stop Temporary Protected Status from being used as a "de facto asylum system."
US District Judge Trina L Thompson had temporarily blocked the administration from cancelling the protections in a sharply worded ruling in July, where she found the government's decision was likely motivated by racial animus.
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