It is illegal to test nuclear weapons on Pluto.
Or Venus or Saturn, for that matter.
And Chile, Uruguay, and the Philippines have been under legal obligation since 1981 to protect the moon's environment from the adverse effects of those countries' nonexistent activities there. The United States and Russia - the only countries that have major space programs - have only agreed to avoid contamination of the moon.
Such is the state of environmental protection in space, where humans are only beginning to venture.
But back on Earth, it's a different story. There are plenty of interests at stake - economic, social, and strategic - so governments have tended to protect the environment only when they see a clear and present danger.
Take the Dec. 1 climate change conference in Kyoto, Japan, where the world's environment ministers will try to set binding targets for cuts in greenhouse-gas emissions. Governments are meeting because, over the past two decades, scientists have come to a consensus that human activities come to a consensus that human activities are altering the world's climate and may result in major disruptions, such as unusual weather patterns and a rise in sea level.
Ten years ago, large holes in the ozone layer were discovered and governments agreed to a phased global ban on the chlorofluorocarbons (CFCs) thought largely responsible. Twenty years ago, concern about the possible extinction of elephants, rhinos, and other creatures led to a 1979 ban on international trade in ivory, rhino horns, and other animal and plant products.
With the growth in awareness of global environmental problems, such agreements are appearing in greater frequency, slowly creating an international body of laws for the protection of the environment comparable to those previously negotiated to prevent warfare.
"The environmental movement started by looking at local problems and soon evolved to national, transboundary, and now global-scale issues," says Eileen Claussen, former assistant secretary of state for science and the environment. "Now, environmental ministers worldwide are increasingly teaming up on important issues to get senior decisionmakers in their governments to take action."
If successful, Kyoto will result in the latest in a series of international environmental treaties negotiated since the turn of the century. The increasing pace and scope of such agreements indicates an important shift in international cooperation, from a focus on issues of war and peace to the preservation of the planet itself.
Negotiating and enforcing international agreements have always been tricky. Unlike national laws, there is no world government to enforce compliance or punish cheaters. Useful agreements require all parties to have a stake in their smooth operation.
Thus the earliest treaties tended to focus on security concerns or improving uses of shared resources.
When the valuable North Pacific seal trade was in danger of following the seals into extinction, the four countries involved - Britain, the US, Russia, and Japan - spent 25 years negotiating a successful 1911 treaty to manage the resource. The US and Canada came to a similar accord in 1916 to protect migratory birds prized by hunters in both nations.
Two world wars and one Great Depression later, the focus was still on managing the commercial harvest of an animal species - this time whales. The major whale-hunting nations agreed in 1946 to form a management body, the International Whaling Commission (IWC), to ensure the long-term health of the industry.
"It was essentially a user's club to protect the users," says Oran Young, director of the Institute for International Environmental Governance at Dartmouth College in Hanover, N.H. "But with the rise of the environmental movement in the 1970s, nonwhaling countries took over the commission and began passing moratoriums on the hunting of many species."
Now the IWC is in danger of falling apart, because Iceland, Norway, Japan, and other whaling states have quit or ceased to comply fully with its preservation-minded pronouncements.
The 1959 Antarctic Treaty has held together, but largely because of the shared security interests of the chief signatories. The landmark treaty - which made the continent a global commons whose environment was to be shared and protected by all - was negotiated because overlapping territorial claims of several nations threatened to lead to military conflict.
Those territorial claims still exist, which gives signatories a compelling reason to uphold the treaty despite increasing pressures to open the continent to industrial fishing, mining, and other potentially damaging activities. The states are now trying to collectively regulate Antarctic tourism, which has grown large enough to threaten the fragile ecology.
Propelled by the growing environmental movement, the 1970s saw an explosion in international agreements to mitigate pollution and protect particular species. "Concern had started focusing more on what we put into the environment, rather than just what we take out," Dr. Young says.
The US and Europe pushed multilateral agreements on marine pollution, wetlands conservation, transboundary pollution, polar bears, nuclear weapons, and trade in endangered species like lions, elephants, and rhinos. Nongovernmental organizations began playing an increasingly important role in formulating policies.
But it wasn't until after satellite images revealed holes in the ozone layer that protects the earth from ultraviolet radiation that governments first negotiated a binding, global agreement to address an environmental concern. First at a Vienna meeting, then in the legally binding 1979 Montreal Protocol, governments agreed to a phased ban on the production of CFCs and other ozone-depleting substances.
"The Montreal Protocol gave people a whole new perspective on what is possible in environmental protection," says Ms. Claussen, who helped negotiate the agreement. "Here's a place where governments got together and moved to deal with a shared problem in a pretty short period of time. It spurred a lot of additional efforts."
One such effort was the 1992 UN Conference on Environment and Development in Rio de Janeiro, which focused attention on worldwide environmental problems. Governments made nonbinding pledges to reduce greenhouse-gas emissions and promote sustainable development policies to integrate economic and environmental goals.
The core documents laid out a comprehensive framework for development practices in the next century, from recognizing the rights of indigenous peoples to the protection and management of forests and rivers. But the summit set few mandated targets or timetables for action.
Five years after Rio, many countries have failed to meet their pledged goals.
"By developing a comprehensive framework agreement for some of these complex issues, governments started focusing on problems they might not have" otherwise, says David Downes, senior attorney at the Center for International Environmental Law in Washington. "Some areas have gotten more attention than others, however." Mr. Downes points to the contrast between climate change and the preservation of biological diversity - two areas considered sufficiently important at Rio that specific treaty conventions were drafted to address each problem. Biodiversity has received far less attention, despite a growing consensus that species are becoming extinct at a pace 100 times as high as the natural rate.
"We're literally standing on the edge of the end of biological history, and our institutions are not prepared to cope with it," Oxford University's Sir Robert May told a meeting of biodiversity experts last month in Washington.
Why is that? Sources say primarily because scientists have yet to reach a focused, international consensus on the scale and likely impact on humanity of the rapid extinction of plant and animal species. Ozone protection and climate change both benefited from the emergence of such a clear scientific consensus that focused public concern and prompted nations to take action.
Agreements at Kyoto could reap important benefits for biodiversity while protecting the climate, according to Howard Ris, executive director of the Union of Concerned Scientists in Cambridge, Mass. Planners are discussing the possibility that developed countries could earn credits toward their treaty reductions in carbon emissions by financing the reforestation of tropical forests, which naturally store carbon.
"Setting aside forests could serve both issues if it's done right," Mr. Ris says. "In theory, you can save habitat and mitigate climate change at the same time."
Some Key International Agreements to Protect the Environment
* Whaling Convention (1946)
Formed by whaling countries to manage whale harvests. As concern for whales increased, nonwhaling states joined in the 1970s and pushed for hunting moratoriums. Its future is in question due to defection of some hunting states and the lack of cooperation by Norway.
Who's in: Ratified by 25 countries to date. The United States, Russia, Norway, and eight other countries have also signed it, but with qualifications. Nine countries, including Iceland and Canada, have denounced it.
* Antarctic Treaty (1959)
Competing territorial claims raised the possibility of an Antarctic conflict. The countries agreed to table their claims, utilize the continent for scientific purposes only, and take measures to protect its environment. It has been successful, but the continent faces new environmental pressures from tourism, fishing, and big science projects.
Who's in: Ratified by the US and 37 other countries.
* Convention on Trade in Endangered Species (1973)
A binding treaty banning or tightly regulating trade in endangered plant and animal species. CITES does not address loss of habitat, the main cause of extinction for most species.
Who's in: It has been ratified by 90 countries. The US and 23 other countries have also ratified it, but with qualifications.
* UN Law on the Sea (1982)
A 400-page treaty setting forth principles, rights, obligations, and acceptable conduct of nations in international waters, including undersea mining, conservation of marine life, ocean dumping, and scientific and commercial activities on the ocean floor.
Who's in: Ratified by 40 countries and signed by 90 others. The US has done neither due to Reagan-era objections to certain sea-floor mining provisions.
* Montreal Protocol (1987)
Aimed to reduce damage to the atmosphere's ozone layer through binding provisions that froze production of chlorofluorocarbons.
Who's in: Ratified by the US and 69 other countries. Entered into force in 1989.
* UN Convention on Environment and Development (1992)
The largest gathering of heads of state in history, the Earth Summit increased public awareness of serious environmental problems confronting mankind, including species extinctions, climate change, and deforestation.
Who's in: The agreements are not binding, and some countries have not met pledges to reduce greenhouse gases and pursue sustainable development.