This chapter discusses: members’ rights and duties under the Companies Act 2006 and the company’s constitution; the problems in dividing power between the company’s members and directors, and the consequences of that division; the rules of interpretation that apply to constitutional documents; the practical exercise of the decision-making powers given to members, including the formalities of meetings and the possibility of informal agreements; the legal constraints on the exercise of power by shareholders; and the enforcement of the constitution by the members, and their potential use of shareholders’ agreements to achieve what they cannot achieve via the articles.