Trump's travel ban is set to take effect Thursday evening — here's how it will be implemented

But the decision included an exemption allowing those citizens to enter if they have a "credible claim of a bona fide relationship with a person or entity in the United States." This prompted some initial confusion, as the justices provided only a few examples of what constitutes a "bona fide relationship" and how a credible claim might be verified.

Here's what we know:

Who can credibly claim a bona fide relationship?

The Supreme Court's order had merely said a bona fide relationship with a person or entity in the US included family members seeking to visit or live with their US relatives, students admitted to American universities, workers hired by American companies, or lecturers invited to speak to American audiences.

The justices noted that two of the plaintiffs in the travel-ban suit sought entry for a spouse and a mother-in-law, both of whom reside in one of the countries included in the ban. The justices said each of those family members "clearly" had a "close familial relationship" and would be permitted to enter, but they didn't delineate how close the familial relationship must be.

But Reaz Jafri, a partner and the head of the global immigration practice at the Withers Bergman law firm, told Business Insider that having too close a relation to a US citizen or resident may actually work against travelers. Federal officials are often suspicious of foreigners who say they are visiting a close relative, believing them to be attempting to unlawfully immigrate to the US under the guise of visiting temporarily.

"This whole close family ties — it's a very dangerous thing to talk about or to use as a basis to get a visa," Jafri said. "My sense is that it just creates massive confusion as to who's going to get in. Only employees, students, people who have had green-card cases processed overseas are going to be let in. Everyone else, in my opinion, are going to be out of luck."

The Supreme Court's decision also explicitly states that people who enter into relationships "simply to avoid" the travel ban are not exempt.

"For example, a nonprofit group devoted to immigration issues may not contact foreign nationals from the designated countries, add them to client lists, and then secure their entry by claiming injury from their exclusion," it says.

Some nonprofits and refugee advocates initially believed refugees who already have ties to US organizations should still be allowed to enter under the court's exemption, but senior administration officials threw cold water on that notion on Thursday.

Ties to US refugee resettlement agencies are not considered to be bona fide relationships, so refugees may only enter if they have family members that qualify as a close familial tie, the officials said.

Who decides whether someone has a bona fide relationship?

The Department of Homeland Security, the State Department, the Justice Department, and the White House have all

Yet it's DHS that is in charge of the border crossings and ports of entry into the US, and its agents are given much discretion when it comes to admitting or denying travelers.

In his dissent, Justice Clarence Thomas said the decision would bring a "flood of litigation" as travelers attempt to discern "what exactly constitutes a 'bona fide relationship,' who precisely has a 'credible claim' to that relationship, and whether the claimed relationship was formed 'simply to avoid'" the travel ban.

It's possible that the full extent of a "bona fide relationship" — especially as it pertains to people claiming a relationship to an entity rather than a person — will not be fully clear until travelers are barred from entry and US parties seek redress through litigation, which Thomas also said was likely to reach the same courts that blocked the travel ban from being implemented in the first place.

Jafri said litigation probably wouldn't occur unless US residents or American companies can prove they've been harmed by the ban.

"If a CBP officer believes that your purpose for coming here is legitimate and bona fide, they'll admit you," Jafri said, referring to Customs and Border Protection. "If they feel it's not, they'll deny you admission. And you can't appeal that. You can't litigate that. You're just going back, and that's it."

In the meantime, Jafri said he was advising clients not to travel unless they have a strong reason for doing so. Those who do attempt to enter, he said, should have documentation that supports their reason for travel. Visitors should show US officials all invitations, schedules, correspondence, hotel reservations, return-flight tickets, and ties to their home countries to prove they intend to return home afterward.

"Hope for the best," Jafri said.

How will this exemption be implemented?

Much about the implementation of such an exemption is still unclear. But DHS said in a statement on Monday that it would "be done professionally, with clear and sufficient public notice, particularly to potentially affected travelers, and in coordination with partners in the travel industry."

Thomas predicted in his dissent that the implementation of such an exemption would be logistically "unworkable."

"Today's compromise will burden executive officials with the task of deciding — on peril of contempt — whether individuals from the six affected nations who wish to enter the United States have a sufficient connection to a person or entity in this country," Thomas wrote.

Some immigration advocates, meanwhile, have predicted chaos. Amnesty International on Monday said it filed a Freedom of Information Act request for documents about how the federal government plans to implement the travel ban.

"The public needs to know exactly what agents in airports nationwide are being told to do, and we need to know now," Margaret Huang, Amnesty International USA's executive director, said in a statement. "This policy is cruel and discriminatory, and it could create havoc in airports in the US and around the world."