Why activists fear little-known treaty could slow fossil fuel phase-out

Vital rulings on the world's energy future are being made behind closed doors and others may be unknown

• ECT poses threat to Paris deal, says whistleblower

The energy charter treaty (ECT) was signed in 1994 to protect the interests of western investors pouring money into the oil- and gas-rich nations of the former Soviet Union. Entering into force in 1998, the treaty generated few cases and even less attention.

That changed in 2014 when investors in the energy firm Yukos were awarded a record $50bn payout after a tribunal found that Vladimir Putin's government had expropriated their assets to prevent Yukos's then chief executive, Mikhail Khodorkovsky, from entering politics. The European court of human rights reached a similar verdict in the same week.