The spouses of H-1B visa holders—who hold H-4 visas—could lose their right to work in the United States under a Trump administration policy change in the works.

Silicon Valley news outlet The Mercury News reported Wednesday that senior leaders in the U.S. Department of Homeland Security have moved a step closer toward final approval of a policy change, part of Trump's “Buy American and Hire American” executive order, that would stop at least some H-1B spouses from working in the country.

If the change goes through, some immigration lawyers say it could hurt American tech companies, which employ many H-1B holders, as it would make the U.S. a less attractive spot for global top talent.

“People could cut their assignments short because the spouse is not able to work, or they might not be willing to accept an assignment in the United States at all because the spouse is not able to work,” said Valentine Brown, a partner at Duane Morris who deals with immigration issues.

Brown said it's easier in many other countries for spouses to get work permits, and top talent may choose to go there from the start.

If H-1B workers already in the U.S. leave—because their spouse doesn't want to live in a place where they can't work, or because the family can't live on one income—employee relocation costs could be high. Companies often spend thousands of dollars sponsoring H-1B workers, a process that takes a lot of both money and time.

“It can be very costly for employers when things like this change,” Brown said. She noted that, in an economy with low unemployment it could also be harmful for employers to lose workers they need to function.

H-4 visa holders' employers should keep in mind these employees may not have working rights in the U.S. should the policy change go through, said Caroline Tang, a shareholder at Ogletree, Deakins, Nash, Smoak & Stewart who works on immigration cases. Employers should know when workers' current permits expire, and be aware of the potential that they'll be un-renewable.

Brown said employers can also have an open door policy for workers concerned about the potential end to H-4 visa work permits, so employees can ask questions and feel secure that the company is staying on top of any immigration law changes.

The work permits are a fairly recent development. Tang noted that the government only began to issue them back in 2015 under President Barack Obama.

“Before [that], a lot of these H-4 spouses just never worked,” Tang said. “They just came to the U.S.—a lot of them would give up their jobs at home—and never be a part of the U.S. workforce.”

In addition to the growing H-4 threat, the Trump White House has also criticized the H-1B program itself. A recent study from the National Foundation for American Policy showed that between the third and fourth quarter of FY 2017 the proportion of H-1B visas denied to foreign-born workers increased by 41 percent.