Solidarity is applicable to multiple strands of European Union (EU) law, including in the fostering of an internal market. Although the internal market has always held constitutional status, the objects that underlie it came about much later. The question of how solidarity, as a principle, value, and concept in EU law has been present in the nurturing of this process is not fully apparent, given a lack of clear methodology for when, and how solidarity is to be utilised. By delving into the treaties and the jurisprudence of the Court, the normative bedrock of solidarity emerges; not just as a facilitator of the internal market, but also for the purposes of economic integration. The article demonstrates that solidarity in law can be a reason or justification for measures to promote the treaty-based aim of the internal market. Yet simultaneously, it finds that solidarity is not an all-encompassing principle, value, or concept in absolute terms, and has limits for utilisation in the spirit of European integration. Conclusively, by demonstrating the limits of solidarity as a ‘legal’ principle, value, or concept, the article asks whether it is time to reassess the role that solidarity should play in EU law in the future.