This article develops a theory of ‘a-legal space’ and its utilization as a political–legal strategy. A-legal space refers to initiatives which adopt a quasi-legal or quasi-institutional form, yet with no official legal basis; a disputed legal basis; or exceeding their recognized legal basis. Examples include unauthorized referenda such as the Catalan independence referendum which took place in 2017 and, on a local level, across Catalonia in 2009–2011; peoples’ tribunals such as the World Tribunal on Iraq, where the US and UK governments were tried for war crimes; and the Aboriginal Tent Embassy where aboriginal activists protesting for land rights erected tents outside the Australian Parliament and declared it an embassy. The use of a-legal space is an under-studied and untheorized tactic employed with increasing regularity by social movement, civil society, and sometimes, state and substate actors. The article builds on the work of political theorist Marta Harnecker, who coined the term ‘a-legal space’, through situating it within the existing philosophical conception of a-legality developed by critical legal scholar Hans Lindahl (2013). The aim is to contribute to an understanding of why citizens undertake these initiatives and how they can have a political impact.