Global public good provision (e.g. environmental quality) confronts us with problems demanding both national and international co-operation. However among sovereign nations reaching agreement on mutual public good provision is difficult. Slowing down global warming is just one example. Due to the diffusion of greenhouse gases in the earth's atmosphere it is attractive for each individual state that other countries commit themselves to climate protection, whereas one's own state using the free-rider-strategy benefits from the protective measures of the others without making any costly national contribution. On the other hand such a strategic behaviour clashes with moral values, especially concerning motives of justice within society. Should free-riding be preferred from the strategic point of view or rather, out of consideration to justice, national commitments to contribute to climate protection? Therefore, an analysis of how appraisals of justice and strategic considerations interact is a challenge to international (environmental) policy. Taking a game-theoretic point of view, we analyse three psychological-empirical conceptions of justice: need, equality and equity, and point out how these principles are able to determine the type of game nations are expected to play.