

So is there a point where he loses everything? If Tesla drops too low, can they call in the debt?
Yes, to whatever extent that Elon-owned stock is pledged as collateral for his personal loans. Loans like that always carry provisions where the lender can call in the collateral if the value drops to a certain ratio of the overall loan balance.
So if Tesla stock plunges enough (and we have no way of knowing exactly how much is enough), that can cascade to where Elon needs to put up some cash, or other property, or pledge more shares, or it all comes crashing down where his collateral gets wiped out at the bottom.
I read your comment to say “the only thing stopping the kill switch is rules,” when I’m pointing out that “the only thing constituting a kill switch is rules,” and those are two distinct ideas that have different implications.