The Trump administration is expected to propose making it harder for legal immigrants to become citizens or get green cards if they’ve ever used public welfare programs such as Obamacare, NBC News reports. Citing four unnamed sources with knowledge of the plan, NBC reports the move is part of White House senior adviser Stephen Miller’s goal to limit the number of migrants who obtain legal status in the U.S. each year. Under the proposals, which are yet to be finalized but have been submitted to the White House Office of Budget and Management, immigrants living legally in the U.S. who have ever used or whose household members have ever used Affordable Care Act insurance markets, children’s health insurance, food stamps, and other benefits could be hindered from obtaining legal status. Immigration lawyers and advocates and public-health researchers told NBC News it would be the biggest change to the legal immigration system in decades and more than 20 million legal immigrants could be affected. The move would not need congressional approval.