In 2016, between Guangdong strikes in mainland China and Hong Kong’s unionization momentum, Hong Kong artist Wong Ka Ying posted a call on Facebook founding the Hong Kong Artist Union (HKAU). The gesture followed the mischievously named Come Inside, Hong Kong’s ‘first female artist duo’ created by Wong and artist Mak Ying Tung, which declared it would combat art’s ‘formalized system’. Ironically, one of its first actions was to enrol in a course on insurance that could help it formalize healthcare for artists. Come Inside welcomed the idea that opposition to the ‘system’ brings artists into it. HKAU took shape within this ‘trap’ when Wong and Mak started researching trade unions. ‘On Union, Displaced’ explores the past four years of HKAU existing as a union-not-yet-registered-as-an-official-union, a serious gesture of ludic conceptualism that plays with artistic freedom’s relationship to captivity and capture. Through Rey Chow’s theory of conceptual art as trap, it traces HKAU’s entanglement in the history of Hong Kong art groups, regional labour organizing, and efforts to reground the term ‘artist’. Studying HKAU requires various conceptual frameworks: Yuk Hui’s cosmotechnics; Laikwan Pang’s multiple sovereignties; Sandro Mezzandra and Brett Neilson’s border-as-method; Linda Lai Chiu-han’s performative research; and Frank Vigneron’s plastician. The article explores how being ‘plastic’ – a union displaced; a union whose registration with the Hong Kong Special Administrative Region is perpetually negotiated – has helped HKAU pose important questions about solidarity and sovereignty in art.