On Sunday night it appeared protesters of Donald Trump’s executive order issuing a broad temporary ban on entries to the US from any national of 7 majority-Muslim countries had scored an early victory. The Department of Homeland Security said it would no longer bar green-card holders from those countries from entering the United States.

The precise language of the DHS statement — which came after a weekend of contradictory statements from other federal officials — was that permanent resident status (a green card) would be a “dispositive factor” in allowing immigrants from those countries into the US during screening.

Given the aggressive way in which CBP agents have enforced the executive order — resisting a federal court order that prevented the deportation of immigrants who’d arrived at US airports since the ban was signed — it remains to be seen whether they will start treating green-card holders from affected countries the same way they treat other permanent residents.

Over the weekend, many permanent residents (green-card holders) were denied entry into the US at the border, or refused to board planes, because they’re nationals of Iraq, Iran, Libya, Somalia, Sudan, Syria, or Yemen — countries that are covered by the 90-day ban Trump signed into effect on Friday night.

The department doesn’t publish statistics on how many people in the US currently hold green cards. But drawing on a ProPublica estimate, based on statistics about who’d received green cards over the last 10 years, we can conclude that up to 500,000 legal permanent residents of the United States might face those additional security checks upon re-entering the country if they left, or if they’re currently abroad. (People are eligible to apply for citizenship after five years as green-card holders in most cases, but many don’t do so immediately — so while some of the people who got green cards a decade ago might be citizens already, there are also probably people who have had green cards for over a decade and now will be affected by the ban.)

In some cases this weekend, green-card holders were allowed to enter the US even if they’ve come from a “banned” country. An administration official confirmed Saturday afternoon that the administration was making “case-by-case” exceptions to allow certain green-card holders into the US.

“We are hearing that some [legal permanent residents] are being admitted after lots of questions” from Customs and Border Protection agents, says William Stock, the president of the American Immigration Lawyers Association.

But the possibility of being able to get into the US by qualifying for a “case-by-case” exception wasn’t exactly reassuring to people who are trying to decide whether it’s safe for them to leave the country. Abed Ayoub of the Arab American Anti-Discrimination Committee called it the “luck of the draw.”

It was not immediately clear on Monday how the new guidance from the administration would change that calculation for green-card holders.

Legal permanent residents, while they aren’t US citizens, are often citizens-in-waiting; they’ve been accepted into the US for life (as long as they don’t commit crimes) and have passed multiple vetting processes. In the eyes of immigration law, however, they are still “aliens” — and therefore, depending on the enforcement of the executive order, they risk being exiled from their homes.