Immediately after which, the Consumer Defense Institute (Idec) and Greenpeace won a court ruling to stop the GMO's release, claiming that CTNBio had acted beyond its powers. And in 1999, a court ruled in favor of Idec and Greenpeace.

After a five-year appeal process, the federal government and Monsanto won recognition of CTNBio's powers to waive environmental studies late this week.

"It's up to the CTNBio to decide on whether an environmental impact study is necessary for the release and commercial use of GMOs," Judge Antonio Ezequiel Silva said in a statement released this week night.

Silva was the last of the tribunal's three judges to vote.

Although backing CTNBio's autonomy he said Monday's ruling would not overturn the earlier court decision in 1999 to stop the release of Monsanto's Roundup Ready soy due to the lack of an environmental study.

Nonetheless, Monsanto released a statement this week afternoon praising the court's decision.

"The decision of the court was an important step in the direction of development for Brazilian agriculture," Richard Greuble, president of Monsanto Brasil, said.

But Greuble added that the company was waiting to see if the constitutional interpretation by the court leads to the creation of definitive rules to regulate the planting of GMOs and the commercial sale and planting of RR soy in Brazil.

Brazil's Federal Regional Court is unlikely to be the end of the issue. Greenpeace and Idec were not immediately available for comment.

In view of the legal confusion, the government last year granted amnesty to planters of illegal GMO soybeans for the current crop.

GMO planting for the next harvest hinges on Congress approval of a Biosafety Bill.

Brazil is the last major agricultural exporter to ban GMO food crops. However in recent years illegal planting of RR soybeans has spread and now covers over 30 percent of the national crop.