I don't believe he was planning to do it arbitrarily. Remember he'd already talked to Jock about the possibility of Ewing Oil becoming a weapon in the divorce and Jock angrily said he'd rather sell it than let that happen. So J.R. (rather uncharacteristically) jumped the gun and started negotiating with Jeremy Wendell to sell the company as if this was a final decision. I believe he expected Jock to agree once everything was worked out and that's when the sale would take place.
We know Jock owned 100% of the company so even if J.R. was the official President I'm sure even he wouldn't have the authority to outright sell the company without the owner's permission.
My understanding is it would be possible but it would require a vote if the shareholders (Jock in this case). I expect that Ewing Enterprises (which seemed to be a holding company for multiple businesses, including EO, until they forgot about it) and EO were incorporated and so each state (depending on the state of incorporation, and it can’t be assumed it was Texas) will have various rules, then theirs federal, SEC, rules if they were public. Still in the end the investors must be consulted and are paramount in protecting their investment. So long way of saying, probably Jock would have to agree and yes Miss Ellie’s lawyers would attempt to either stop it or make sure the sale was at least not shorting her. It would be messy. Then if trusts were involved, and they almost always are, even Jock might not have control. It gets really messy and tv, at least back then, wanted simple.
If you want good show that deals with corporate ownership, especially a public company, Secession is pretty good. I’m not as familiar with the law here to say they’re spot on, but it’s close enough for me not to question anything. They seem to be to be based on the Ford family combined with maybe the Gettys and a few others.
Investing can be done well as a family when the family dynamic is healthy, like the Waltons (not perfect but not dysfunctional). But when a family is full of dysfunction, it starts at the top and works it way through out, it’s only a matter of time until they loose that money and power - that’s fun to watch - like the Vanderbilt’s.
As for the Fords, Henry and his only child Edsel were as dysfunctional as you see in succession. But it appears Edsel’s children were functional enough to keep it together, diversify their well, keep control of their company going on the 6th generation, and for control of a top 30 company I’d say that’s pretty functional. Though they did walk away from the foundation, which is among the top 10. Makes for some good drama anyway. For me the best drama is believable in what we see.