A question yesterday, Can a company refuse to sell stock?, had asked about if a company could prevent sale of its stock to certain parties. The accepted answer was that, no, a company can't put restrictions on its stock because shareholders already own it, not the company.
Is there a situation in which a company could control its stock through contractual agreement? Two cases:
The company is still privately held. It agrees to sell its stock to third parties under the condition that those buyers agree to terms and conditions regarding how they are allowed to trade that stock. These terms and conditions include that new buyers also have to agree to the same terms and conditions.
A company is already public, but its shareholders unanimously agree (crazy, right?) to enter into an arrangement in which they must each trade their stock according to some protocol, e.g. say as approved by a majority vote of the then-current owners.
Naively, it seems that both of these arrangements are simple contractual agreements. But, it seems plausible that such arrangements might be barred by regulation.
So, in the US for publicly traded companies, can a company control its stock through contracts with stockholders? Or are such arragements prohibited by regulation?