China, the world’s largest importer of wood, has amended its forest law to include a nationwide ban on the purchasing, processing and transportation of illegally sourced timber, according to the Environmental Investigation Agency (EIA), a U.K.-based nonprofit that investigates environmental crimes.

The country’s forest law was last updated 20 years ago.

“This is potentially huge, a real game-changer for both the future of the planet’s precious forests and the battle against dangerous climate change,” EIA Forests Campaign Leader Faith Doherty said in a statement. “For almost 20 years, China’s demand for raw materials for its vast wood-processing industry has been a massive driver of illegal logging around the world, especially in Southeast Asia and Africa.”

China is also the largest exporter of wood-based products in the world.

In 2013, the United Nations reported that 15–30% of all timber traded globally was harvested illegally.