The concept of emissions trading has been actively debated by economists since the 1960s (Dales, 1968; Voss, 2007). In the 1990s, it began to attract the attention of large businesses in the EU, who were eager to investigate whether it offered a politically more palatable alternative to the Commission’s default policy instrument – regulation. By the late 1990s – and buoyed by growing industry support – a small number of Member States began to adopt their own greenhouse gas trading schemes at the national level to bolster their existing policy instrument mixes which, at the time, were also heavily reliant on regulation and, in some cases, voluntary agreements (Wurzel et al., 2013). The early 2000s were a period of intense activity for EU climate and energy policy, much of it directed at implementing the EU’s increasingly ambitious long-term emission reduction goals (see Chapter 3). Internationally, emissions trading had been included in the recently ratified Kyoto Protocol. With other policy instrument options such as an EU carbon/energy tax seemingly unavailable, the Commission seized the opportunity to create an EU-wide trading system.