Billionaire Elon Musk’s offer to pay TSA personnel during the partial government shutdown poses “great legal challenges,” according to the White House.

The world’s richest man recently shared a social media post offering to pay TSA employees amid the Department of Homeland Security shutdown, which began in mid-February after lawmakers failed to reach a deal on funding the agency. TSA employees are working without pay which has led to staffing shortages and long security lines at airports nationwide.