A U.K. Supreme Court jury has found the CEOs of two major oil and gas companies guilty of “ecocide” for their role in extracting crude oil from Canada’s tar sands.

The mock trial, Ecocide v. Living Planet, was a part of campaign to have ecocide recognized by the United Nations’ International Criminal Court as the fifth crime against peace — along with genocide, war crimes, crimes of aggression and crimes against humanity. The trial featured real lawyers arguing their case before a jury at the U.K. Supreme Court and featured testimony from expert witnesses. The CEOs of the companies were portrayed by actors.

The CEOs of Global Petroleum Company and Glamis Group, both fictional companies, were convicted on charges that related to oilsands operations in Alberta. However, one was acquitted of charges relating to the 2010 Deepwater Horizon oil spill. Expert witnesses testified that the Gulf of Mexico had become a “dead zone” after the oil spill and Michael Mansfield, lawyer for the prosecution, claimed the spill had injured or killed 4,000 birds.

“Companies cannot be given a licence to spill and kill as they clean up the mess,” Mansfield said.

Ecocide is the creation of British lawyer Polly Higgins, an environmental legal expert. In April 2010, Higgins asked the UN Law commission to recognize ecocide in order to create an obligation for companies to avoid harming the planet.

“Ecocide is the extensive damage, destruction to or loss of ecosystems of a given territory, whether by human agency of by other causes, to such an extent that peaceful enjoyment by the inhabitants of that territory has been severely diminished.”

According to a blog on Care2, a 2010 report for the United Nations found that 3,000 of the world’s biggest corporations caused $2.2 trillion of ecocide in 2008.

If the UN accepts Higgins’ proposal, the law could impact how industries, corporations and countries conduct their business. An ecocide law could force companies to abandon chemicals that contaminate soil and water, end the process of large-scale deforestation and force traditional energy companies to embrace green and clean energy technologies. The most controversial section of the law would make company directors, and not the company itself, criminally responsible for environmental damage.

The deadline for final wording on the law is January 2012, with a vote on other amendments expected later in 2012.