Background: EU environmental legislations affecting global supply chains have come into force since 2022. As procurement plays a direct role effectuating this, the result of these legislations via procurement becomes relevant. Methods: A systematic literature review is used to synthesize 152 articles from managerial, business administrative, and supply chain journals. The Context–Intervention–Mechanism–Output framework (CIMO) is used as the lens by which the articles are analyzed. The articles present findings from diverse methodologies and combine green business-to-business procurement with at least one element from the CIMO framework. Results: Five conceptual frameworks of different green procurement strategies are developed, each explaining the strategy and its expected result. The strategies increasingly collaborate and by this increasingly reduce environmental impact. A comparison of the strategies identified variables which strengthen the working of environmental legislation as they contribute to collaboration. Conclusions: Customer demand is crucial for collaborative green procurement. Without this, environmental legislation will only achieve limited environmental objectives. Propositions are formulated on variables which, next to the business case, strengthen the working of environmental legislation. This article adds to the science by synthesizing the existing knowledge base into propositions and future research directions. The findings may also support policymakers in understanding the effectiveness of legislation.