For many of the young undocumented immigrants whose futures have seemed to be hitched to a roller-coaster in recent months, Wednesday was a day of unusual hopefulness: The night before, a federal judge had signaled his readiness to open applications once again for a program that protects some young undocumented immigrants, known as Dreamers, from deportation and allows them to work.

“First thing this morning, I opened up my email to find inquiries from potential applicants. We’re telling them to get all their paperwork together, let’s get ready,” said Fernanda Durand, communications manager at Casa, an immigrant advocacy organization. “This is the first ray of hope that these Dreamers have had in a very long time.”

Not so fast, she had to tell her clients. Judge John D. Bates of the Federal District Court in Washington wasn’t going to make his order effective for 90 days. Much could change in the meantime. It might not happen at all.

Since the early days of the 2016 presidential campaign, young people who benefited from the Obama-era program, Deferred Action for Childhood Arrivals, or DACA, have seen their hopes alternately elevated and dashed, sometimes in the space of a single week. President Trump canceled the program, some judges revived it, politicians negotiated deals to save it — but none of them closed.