Most federal employees have a union contract.
Herr Diktator Biden can issue orders until the cows come home.
AFGE is gonna crush him like a bug. They take their union contract _very_ seriously, and they _own_ the Democratic Party.
670,000 members.
https://en.wikipedia.org/wiki/American_Federation_of_Government_Employees
But they might go along with Biden if they think the mandates will destroy capitalism and speed up the Revolution.