Global environmental governance has expanded significantly, yet it remains politically inadequate to address planetary crises in the Anthropocene. Despite the proliferation of multilateral environmental agreements, governance arrangements continue to suffer from fragmentation, weak authority, limited accountability, and a sovereignty-bound logic that constrains collective action. This article critically examines these limitations through an assessment of polycentric and Nested Systemic Governance approaches. While nested governance can reduce fragmentation and enhance participation, it remains dependent on voluntarism and lacks the political authority and democratic anchoring required for durable coordination. Drawing on debates in environmental politics and global governance, the article advances a longer-term institutional perspective that conceptualises a gradual evolution toward a federative framework combining multilevel participation with enforceable authority and democratic legitimacy.