Thousands of foreign workers who came to the U.S. as students could be forced to leave the country, depending on the outcome of a court hearing in Washington on Thursday. The U.S. Department of Homeland Security has asked a federal judge for more time to write a new rule allowing some recent graduates to remain in the country to work in science, technology, engineering and math (or STEM) jobs.

The Optional Practical Training program allows foreign students and recent graduates to gain work experience in their fields of study. Students in all majors can work for up to a year. Those with degrees in the STEM fields can apply to work for up to 17 additional months.

“A lot of them are doing important research projects, they’re working with grants, where it’s generally more than a one-year project,” said immigration lawyer Emily Neumann, who represents foreign workers seeking long-term visas.

Last August, a federal judge nullified the so-called STEM extension, but gave Homeland Security six months to come up with a new rule. The grace period expires February 12, but the government has asked for more time to wade through the more than 50,000 comments it received on its proposed new rule.

“Students are very tense right now, not knowing if less than a month from now they’re going to be forced to leave the country,” said Neumann.

The STEM extension is being challenged by a group of high-tech workers who say it takes jobs from Americans.

“This OPT extension was specifically designed to circumvent the limits on foreign workers,” said John Miano, an attorney representing the workers.

The proposed new rule would increase the STEM extension to two years beyond the initial 12-month period, but it offers some protections for American workers. Employers would have to agree not to fire or lay off any U.S. workers as a result of hiring a foreign-born worker, and would have to pay similar wages.

Those safeguards aren’t strong enough, said Miano.

“There’s no enforcement provisions whatsoever and no penalties, so if employers simply ignore them, nothing happens,” he said.

If the government’s own extension is approved, it will have until May to finalize the new rule.