Major immigrant activist groups in New York City have called a rally for Thursday evening to protest a revised version of President Donald Trump's travel ban before it takes effect at 8:00 p.m.

The latest version of the travel ban, impacting refugees and nationals of six majority-Muslim countries, could bar certain relatives of US citizens whose relationships are not deemed adequately "close," including grandparents and grandchildren, from applying for US visas, according to a State Department memo first acquired by the Associated Press.

Aunts and uncles, cousins, in-laws and fiances of US citizens traveling from the impacted countries—Syria, Sudan, Somalia, Libya, Iran and Yemen—would also be barred from visa applications. [See below for update.]

Only applicants with a parent, spouse, child, son or daughter-in law, or sibling in the US could apply under the rules, according to the AP. The new restrictions will be in place until the Supreme Court hears arguments on the travel ban this October. Anyone with a scheduled visa appointment can keep that appointment, according to administration officials.

"Donald Trump does not get to decide who is family or what is love," the advocacy groups wrote on Facebook, calling on protesters to gather in Union Square at 5:30 p.m. "It's up to us now to fight back against this latest attack and stand up for the values that truly make America great: opportunity and justice for all."

Already today, immigration lawyers are on the ground at John F. Kennedy Airport, preparing to help travelers navigate new rules they say have sown confusion. The refined guidelines impacting certain relatives were reportedly shared with US embassies and consulates late Wednesday. They are the State Department's interpretation of guidelines issued earlier this week that require travelers to demonstrate a "bona fide" relationship to a US citizen or institution in order to enter the country.

Trump's executive order bars refugees for 120 days, with exceptions. The Supreme Court decision applies the "bona fide" rule to refugees, as well. According to the NY Times, about 40 percent of refugees bound for the US have no family ties here.

The Supreme Court guidelines also suggest that anyone who is traveling to the US for school or for work, or has an arrangement with a refugee resettlement program should not be barred, attorneys said. But they cautioned that these latest consulate orders could prove chaotic, representing an overly-narrow interpretation of the Supreme Court guidelines.

"The fact that we are here trying to figure out what the Supreme Court's intent was because the White House is not following it is insane," said Camille Mackler, director of legal initiatives for the New York Immigration Coalition, which is organizing tonight's action. "It's such a slap in the face to our courts and institutions."

Reached for comment, the State Department directed Gothamist to a background call with senior White House officials. "We expect business as usual at the ports of entry starting at 8:00 p.m.tonight," officials said.

Hasan Shafiqullah, a Legal Aid Society attorney, said that the latest travel ban likely will not play out in full view to New Yorkers at NYC airports like it did in January. Instead, families and individuals will face complications at US consulates and embassies.

"Consulates operate in darkness. Nobody knows what happens there. You're not allowed a lawyer until you are inside the United States," Mackler said at a panel on the travel ban at BAM on Wednesday night.

In the US, citizens will not be able to have certain family members attend weddings, graduations, funerals.

The possibility for airport issues is also there, especially early on, lawyers predicted.

"Say you have a nice person at Delta who says... welcome aboard.' And then you get to JFK and Customs doesn't think the relationship is bona fide enough, and tries to get you on the next plane back," Shafiqullah said.

"We're now forced to quibble over [family] relationships," he added. "The first [travel ban] everyone was kept away, and it was way over-broad. Now it's been narrowed down and the government says it should withstand legal scrutiny. It may be harder to challenge, but it is still motivated by unconstitutional bias."

The confusion could impact many more travelers than those the travel ban targets, Mackler added.

"When we were at JFK the first time [in January], we weren't just helping people from those seven counties, we were helping people from 30 countries," she recalled. "I had a kid come to me from Jamaica who was too afraid to travel on spring break because he was afraid he wasn't going to be let back in."

This story has been updated with additional context from a background call with senior White House officials.

[Update June 30th]: The State Department said Thursday night that fiances qualified as 'bonafide' under the Supreme Court guidelines, amending earlier guidance.