Judges on the U.S. Court of Appeals for the Fourth Circuit on Friday questioned the changing interpretation of a “public charge” under a Trump administration immigration policy and whether they had the authority to permanently define it.

A lawsuit brought by Georgetown Law’s Institute for Constitutional Advocacy and Protection, on behalf of the group Casa de Maryland and several immigrants, challenged the administration’s rule issued last year that makes it more difficult for noncitizen immigrants who receive public benefits to become permanent legal citizens. The challengers argue that impacted immigrants are withdrawing from benefits they need, such as food stamps, in order to meet the requirements.