Climate change is a global environmental problem which has been addressed primarily at the multilateral level. However, national, supranational, and even subnational action on the issue has also sprung up. At the subnational level, California (United States) and Acre (Brazil) offer an interesting example of how domestic policies may be linked in order to address climate change. Based on a memorandum of understanding concluded in 2010, these two states have been working towards the possible linkage of their respective climate change policies, in essence providing a pathway for using emissions offset credits that are generated in Acre through reductions of forest-based emissions in the Californian cap-and-trade programme. Taking into account that this is an ongoing process, this commentary provides a general overview of the issue from the perspective of international law.