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system
can a company control its stock through contracts with stockholders?
user
your first scenario, involving shareholders in a private corp being limited by a contractual agreement, is common in practice. frequent clauses include methods of valuing the shares if someone wants to sell, first right of refusal [you have to attempt to sell to the other shareholders, before you can sell to a 3rd party], and many others. these clauses are governed by contract law [ie: some clauses may be illegal in contract law, and therefore couldn't be applied here]. a universal shareholders' agreement is just the same as the above, but applied to more people. you would never get an already public company to convert to a universal shareholders' agreement - because even 1 share voting 'no' would block it [due to corporate law limiting the power of a corporation from abusing minority shareholder value]. in practice, these agreements universally exist at the start of incorporation, or at least at the first moment shares become available. an example is the canadian mega-construction company pcl*, which is employee-owned. when the original owner transferred the corporation to his employees, there was a usa in place which still today governs how the corporation operates.  in theory you could have a 'public company' where most shares are already owned by the founders, and 100% of remaining shares are owned by a specific group of individuals, in which case you may be able to get a usa signed. but it wouldn't really happen in practice.  *[note that while pcl is broadly owned by a large group of employees, it is not a 'public company' because any random schmuck can't simply buy a share on the toronto stock exchange. i assume most exchanges would prevent corporations from being listed if they had ownership restrictions like this].
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