"Quartering Troops" sounds archaic, but every now and then lawmakers propose it, like forcing private airlines to provide discounted or free arrangements for servicemen traveling. (As opposed to negotiating rates with them, or soliciting competitive bids). These proposals usually don't get very far, but it shows you that the Government still thinks it's OK to _force_ a citizen or private business to give free services or accommodations to soldiers.
(For example, see https://www.huffingtonpost.com/2011/06/08/congressman-bruce-... and https://www.huffingtonpost.com/2011/06/08/delta-troops-afgha... The Government should reimburse him, and try to negotiate the best rates from the Airlines. I'd be all for the Airlines offering a discount, but they shouldn't be forced to.)