My mind is blown by how the US Federal Government can claim someone is essential and force them to work without pay. I've read a pretty good explanation of it

My mind is blown by how the US Federal Government can claim someone is essential and force them to work without pay. I've read a pretty good explanation of it here: https://www.washingtonpost.com/outlook/2019/01/11/how-can-government-force-people-work-without-pay-indefinitely/?utm_term=.6295e1aeb370 https://www.washingtonpost.com/outlook/2019/01/11/how-can-go... Yet, I still cannot understand how it is legal to make people work without pay based on an Attorney General's thoughts on it in the 1980s. Amazing.