In this Aug. 17, 2018, file photo, people arrive before the start of a naturalization ceremony at the U.S. Citizenship and Immigration Services Miami Field Office in Miami. AP-Yonhap

WASHINGTON — President Donald Trump last year dramatically ratched up the fee for H-1B work visas to $100,000 , saying it would protect American workers from losing their jobs to lower-paid foreigners.

But on Monday a federal judge struck down the fees, siding with 20 states and ruling that the Trump administration exceeded its authority by raising the fee without congressional approval.

Many tech companies and universities rely on the H-1B program to fill openings for skilled jobs, and universities use it to lure top researchers. But critics charge the visa program has been used to replace American tech workers. Here’s a look at the visa program, Trump’s fee and the court’s decision.

What are H-1B visas and who uses them?