As noahc says, this question is too vague to be useful. But here's some examples of rules regarding stock transfer. If you're in the US and talking about stoc

As noahc says, this question is too vague to be useful. But here's some examples of rules regarding stock transfer. If you're in the US and talking about stock in a private company, stock is often "not transferable". You can choose to sell it, but you might only be allowed to sell it to current investors, and the company might have a clause that says that if you try to sell it to someone they don't want you to sell it to then they have the option to buy it instead of the other person, and there's all kind of things like rights of participation that are designed to keep ownership percentages in line, and it's very complicated. Note that these examples are not illegal, they're just disallowed by the terms set by the company that you acquired shares in. When you acquire the shares, you agree to the terms.