NLRB already mandates OT for hourly workers, that's why so many low level "supervisors" and "managers" get put on salary and then worked 60-70 hour weeks for a 40 hour salary. Happened to me in the '70s with TRW (I left) and is happening to son-in-law today in transportation.
I've lost count of how many people I've known who refused promotion because they'd lose too much money just to gain a meaningless title.
(Also reminds me of a time long ago when promotion to O4 meant just enough pay raise to throw a decent promotion party.)
As to the how was it done...I'm not knowledgeable enough to speak on labor laws vs regulations & I wasn't in on any of the alleged talks leading up to this but it sure rings of "stroke of a pen" rule.
If we had an economy worth a d***, people who felt a company was abusing them by imposing too heavy a workload could just go elsewhere.
The problem I see with this rule is that it kills the salaried person willing to voluntarily work long hours to get ahead in the company. That was always my route to whatever success I had...
This country is going to be left with no work ethic at all, as is intended, I suppose.