Concern about international environmental governance has shifted from the problems in having multilateral environmental agreements adopted to trying to ensure that the agreements which are negotiated are implemented, and that they produce positive environmental outcomes. This article argues that features of the international policy process which assist domestic policy adoption, especially scientific reductionism and moral suasion, can undermine the chances of policy implementation. This is often because business interests which are marginalised during policy adoption are more influential at the domestic level at which policy must be implemented. This asymmmetry is explained by suggesting that — rather than their being ‘two‐level games’ (as Putnam suggested) — there are (in Lowi's terms) distinctive arenas of power at the the international and national levels. Improving policy effectiveness requires the distribution of power in each arena to be made more symmetrical.