There's no provision to expel a member state, but TEU Article 7 delivers to the suspension of particular legal rights. Launched from the Treaty of Amsterdam, Article seven outlines that if a member persistently breaches the EU's founding concepts (liberty, democracy, human legal rights and so on, outlined in TEU https://elliotrhmch.ampedpages.com/a-secret-weapon-for-link-member4d-56870878