Some States party to the agreement may meet domestic NDC targets through establishment of emissions trading regimes. As of 2015, 35 countries and 22 cities, states and regions have established some form of emissions trading scheme.5 The Paris Agreement will recognize traded credits when such domestic emissions trading programmes link and arbitrage credits between themselves. Trading member states will be able to determine domestically what constitutes an emissions credit, but trade in such credits between member states will have to meet UNFCCC established guidelines. Shared standards will ensure that credits with different emissions values can be harmonised, and help to prevent double-counting between a state producing emissions reductions and one acquiring them.