A key international agreement on protecting the Earth's myriad species against any risk from biotechnology will soon come into force.
By Alex Kirby
BBC News Online environment correspondent
The agreement, the Cartagena Protocol, is part of the United Nations Convention on Biological Diversity (CBD).
It will allow countries to reject imports of genetically-modified (GM) goods if they can cite valid scientific reasons.
But experts fear the protocol may clash with World Trade Organisation (WTO) rules.
The protocol will enter into force 90 days after 50 signatories have ratified it. So far 49 have done so.
It commits member states to ensure the safe transfer, handling and use of what it calls LMOs, living modified organisms, known also as genetically modified organisms.
At its heart is the concept of "advance informed agreement" (AIA), a procedure designed to make sure countries have the information they need before agreeing to import GMOs.
The protocol will also establish a biosafety clearing-house, in the Canadian city of Montreal, as a one-stop shop for information on GMOs.
Any country wishing to export GMOs has to notify the clearing-house, so the recipient country can obtain the information it needs to decide the case.
It sounds simple enough, but there are real fears the protocol could fall foul of the WTO.
There was heated debate at the Johannesburg World Summit on Sustainable Development in 2002 over the relationship between the WTO and multi-lateral environment agreements like the protocol.
Anti-GM protests continue
In principle they enjoy equal validity, but campaign groups believe the developed countries' drive for trade liberalisation will mean the WTO always triumphs in the end.
One reason allowed by the WTO for the management of trade is the existence of scientific evidence supporting an objector's case.
In contrast, the protocol emphasises a precautionary approach, though it does say countries objecting to GM exports must do so on the basis of a scientifically sound risk assessment.
Dr Klaus Toepfer, the executive director of the UN Environment Programme (Unep), believes the protocol is compatible with the WTO.
Balance of evidence
He told journalists in London: "I'm fighting for the idea that the precautionary approach does not give carte blanche to refuse a scientific assessment.
"Precaution is not anti-scientific. All it means is, in future, importers must be able to say no, even if their scientific knowledge is not complete.
"We need sounder science, but we can never have full knowledge. I may be too optimistic, but I really believe this will mean a huge change in the way we handle the subject."
The protocol may hearten GM's opponents
Dr Toepfer told BBC News Online: "The protocol puts the power of refusal in the hands of countries asked to accept imports.
"In that sense, it's also going to be binding on countries which don't ratify it. They'll have to accept a scientifically-argued case."
Changing its spots
Konrad von Moltke, of the International Institute for Sustainable Development, told BBC News Online: "The issue is the quality of the legal work at the WTO.
"If that's well done, then it will be apparent there's no question of either the WTO or the protocol assuming priority over the other.
"There've been interesting developments in the WTO dispute settlements procedure. I think there's a chance this will work, though of course there's always some uncertainty.
"The situation in the WTO is markedly different now from what it was five years ago."