Under 6 USC 1523: Federal cybersecurity requirements [1], as well as a recent White House Executive Order [2], that would be my interpretation. ~211 federal agency applications support Login.gov, so I have a bit of curiosity in the outliers, especially when public facing.

[1] https://uscode.house.gov/view.xhtml?req=granuleid:USC-prelim...

[2] https://www.whitehouse.gov/briefing-room/presidential-action...