In general, shareholders can only be forced to give up or sell shares if the articles of association or some contractual agreement include this requirement.
In practice, private companies often have suitable articles or contracts so that the remaining owner-managers retain control if an individual leaves the company. In such circumstances, the employee or director may, dependent on the circumstances in which he or she has left, be entitled to receive a 'fair value' for the shares - often determined by the company's accountants - or may merely be entitled to the nominal value of the shares (eg £1).
The shareholder may have a claim against the company or the other shareholders if they can show that they have been unfairly treated.
