This article considers the issue of normative limits of peace negotiations as set in the existing international guidance for peace mediators. Tensions between the aim for peace, justice and the protection of human rights in the crafting of conflict settlements have been of increasing concern. Over the past decade the United Nations (UN) has been at the forefront of informing and guiding mediators on the normative limits of peace agreements negotiated under UN auspices. This article provides an overview of UN guidance addressing normative aspects and explores how these can impact on the negotiation process. It then proposes questions for further reflection on this growing trend. Ultimately the article argues that understanding the role of normative factors, especially legal parameters such as international human rights law and minority rights, can help to strengthen the legitimacy and credibility of peace processes and their outcomes.