In recent years, internal displacement has emerged as one of the most pressing humanitarian, human rights and political issues facing the international community. The situation of internally displaced persons (IDPs) can be described as falling into a vacuum of responsibility within the state. The principle of state sovereignty limits the ability of the international community to provide them with assistance and protection. This has lead to institutional gaps in international law when it comes to the protection of IDPs, and constitutes a protection gap. My aim with this thesis has been to answer in which ways the subject of internal displacement and the protection gap challenge the principle of sovereignty and the mandate of the United Nations High Commissioner for Refugees (UNHCR), in addition to raising awareness of over 25 million uprooted people. The subject of internal displacement has presented the international community with new issues to deal with. Normative developments have taken place, in the sense that there is more pressure on a sovereign state to behave responsibly. This calls for an involvement of the international community to supplement the efforts of local and national authorities. In addition to a more restrictive asylum-policy, these normative developments has had both political, principle and practical implications for the work carried out by the UNHCR, with an increase of in-country protection as a result. I included Colombia as an empirical manifestation of reality. Colombia has over two million IDPs, which is fourth highest in the world. Legally, the state of Colombia is a responsible sovereign state, doing everything "right" with the most comprehensive and judicially advanced IDP legislation in the world. However, politically, the Colombian state’s sovereignty is questionable when implementation of IDP law is absent.