In implementing the Green Deal to align with the Paris Agreement, the EU has increased its climate ambition and is currently negotiating how the increased mitigation effort should be distributed among Member States. Such partitioning of targets among subsidiary entities is becoming a major challenge for implementation of climate policies around the globe. We contrast the recent EU Commission proposal - an ad-hoc decision based on a singular country attribute - with transparent and reproducible methods based on three ethical principles. We go beyond traditional effort-sharing literature and explore allocations representing an aggregated least regret compromise between different country perspectives. While the current EU proposal represents a nuanced compromise for many countries, for others a further redistribution could be considered equitable. We demonstrate the applicability of our approach for the necessary modifications to the effort sharing targets for 2030 among EU Member States.