The Mental Capacity Act 2005, and the domestic law surrounding it, is currently in a state of instability, having undergone rigorous scrutiny by the House of Lords Select Committee. At an international level, the United Nations Convention on the Rights of Persons with Disabilities 2006 has cast substantial doubt over the very basis of this legal framework. The recommendations made by the Select Committee, and any resulting action by the government to address these, will be hoped to have an impact on the implementation of the legislation on those falling within its remit. On a deeper level, however, this thesis seeks to critically engage with the theoretical underpinnings which inform and guide this legislative framework. This entails a questioning of the ways in which those with disabilities and their carers are responded to under the statute. Exploring the theoretical debates in this context leads to a conclusion that the Act promulgates an individualistic approach to the concept of mental capacity, and does not adequately reflect the reality and lived experiences of those deemed to lack capacity or their informal carers. The papers in this thesis interrogate these issues through a focus on three distinct areas- carers interests under the best interests test; the Deprivation of Liberty Safeguards though a social model lens; and capacity to consent to sex. In doing so, this thesis suggests that more relationally and contextually focused approaches can inform a legal framework which is attentive and responsive to the interwoven interests of those with cognitive impairments and their carers, and which facilitates the enjoyment of rights through a focus on the societal, structural and institutional barriers which have historically worked to exclude these individuals.