On any given day, the U.S. Court of Appeals for the D.C. Circuit has the power to throw the environmental movement into complete disarray.

Tucked into a nondescript neighborhood in Washington, D.C., the court isn’t well known to the public, but it’s often called the second most important court in the United States. It has particular significance to the environmental movement because of its exclusive jurisdiction over regulations involving vital environmental laws like the Clean Air Act, the Clean Water Act, and the Endangered Species Act.

In the early stages of the modern environmental movement, great progress was made through enterprising lawsuits brought by groups such as the Natural Resources Defense Council and Environmental Defense Fund to enforce the protective mandates of those landmark environmental statutes. But the challenge is different now, with judges on the bench seeking to derail, not enforce, these fundamental safeguards. How environmentalists respond to this threat could dramatically impact the success of the movement in combating 21st century environmental threats such as global warming.

Indeed, with Congress paralyzed by gridlock, the only path forward for effective responses to climate pollution is through administrative implementation of the Clean Air Act — which the Obama administration is vigorously pursuing. But that option is available only because of a 5-4 Supreme Court decision in 2007. In Massachusetts v. E.P. A., the court held that the act, as currently written, empowers the Environmental Protection Agency to regulate pollutants that cause global warming. The EPA is moving to exercise this authority, but the fate of all its regulatory initiatives will be evaluated, and in large measure determined, by the D.C. Circuit.

The court holds the cards on many environmental issues. Indeed, in the first two weeks of this month alone, the court is hearing cases involving emissions standards on sewage sludge incinerators, challenges to EPA rules requiring states to address greenhouse emissions in their permitting requirements, emissions standards for hazardous pollutants resulting from lead processing, and even a pair of cases regarding the importation of polar bear hunting trophies.

These cases sometimes go very badly for environmentalists. In October of 2012, after a 2-1 D.C. Circuit majority overturned EPA’s “Good Neighbor” rule — which constrained individual states’ contributions to air pollution in neighboring downwind states — Pulitzer Prize-winning Washington Post columnist and George Mason University professor Stephen Pearlstein observed that “dysfunctional government has become the strategic goal of the radical fringe [on the political right]. … Nowhere has this strategy been pursued with more fervor, or more success, than the U.S. Court of Appeals for the District of Columbia Circuit, where a new breed of activist judges are waging a determined and largely successful war on federal regulatory agencies.”

As Pearlstein makes clear, cases are not decided by the court as an institution; they are decided by the judges who sit on that court. And there has been a concerted effort by conservatives to dominate the federal bench, and this bench in particular. Look no further than Senate obstruction of President Obama’s judicial nominees to the D.C. Circuit. Republicans have already led a successful filibuster against Caitlin Halligan, a highly qualified D.C. Circuit nominee who ultimately withdrew her nomination after more than two years of obstruction. Now they have introduced a bill to reduce the number of seats on the D.C. Circuit from 11 to eight in a nakedly partisan attempt to maintain conservative dominance over the makeup of the court.

President George W. Bush appointed three of the court’s seven currently active judges, Bill Clinton appointed three, and George H.W. Bush appointed one. President Obama has yet to make a successful appointment, despite four of the seats being vacant. But that does not tell the entire story. Many federal courts rely on judges who have taken “senior status” — a form of semi-retirement that involves still hearing cases — to help manage caseloads. Five of the court’s six very active senior judges are appointees of Ronald Reagan or H.W. Bush, and these firebrand conservatives continue to make their mark in environmental cases.

It is time for the environmental movement to involve itself more in the conversation about nominations. There is no downside to supporting well-qualified nominees to the bench and opposing mindless obstructionism. It’s also important to make clear that the environmental community doesn’t need treehuggers on the bench; it only needs judges who will follow the protective mandates of the statutes passed by Congress.

When it comes to addressing the nation’s 21st century environmental problems, environmentalists must pay far more attention to the third branch of government — a branch, after all, that is made up of people who are appointed not for four or six years, but for lifetime terms. The future of environmental law is inextricably linked with the future of the federal bench.

For more on the D.C. Circuit and its importance, see “Broken Circuit: Obstructionism in the Environment’s Most Important Court” [PDF], the cover story in the latest issue of The Environmental Forum.

If Congress and the president fail to tackle global warming, can courts step in? Can federal judges allow people struggling with the losses of global warming to sue polluters directly?

The idea may at first seem crazy. In a legal world obsessed with claims of judicial activism, the image of a judge taking on a global problem like climate change seems like the punch line to a bad joke at an Exxon board meeting. But it turns out there is a long and proud history of judges addressing pollution in the absence of environmental regulation. For much of the last century — long before Congress acted — federal courts allowed plaintiffs to seek injunctions to stop all kinds of pollution. Successful suits prevented an ore smelter from releasing deadly atmospheric arsenic over the homes and families of Utah, the City of Chicago from draining its sewage into St. Louis’ drinking supply, and New York City from dumping its garbage into the Atlantic, where it washed up on the beaches of the New Jersey Shore. Today, states and environmentalists are turning to these and other historic precedents to make the case that climate change, too, belongs in the courts — when the other branches of government refuse to act.

The current battle began in 2004, the midpoint of the Bush presidency. A coalition of states and private land trusts, led by the State of Connecticut, that were frustrated with Washington’s failure to introduce legislation or regulations limiting greenhouse gas emissions sued several of the nation’s largest electric utilities in Connecticut v. American Electric Power. The coalition alleged that the companies’ greenhouse-gas emissions amounted to a “public nuisance” in the form of global warming. Under the nuisance principle — one of the oldest in English common law — a property owner may ask the court to stop a defendant who is interfering with the owner’s enjoyment of his own property, and, in some circumstances, to pay damages. In the Connecticut case, the plaintiffs thus sought to persuade the court to order the utility companies to reduce their greenhouse-gas emissions by showing how such gases cause global warming, which in turn was creating increased temperatures, alternating drought and floods, destruction of natural habitats, and corresponding decreases in property values and human health and welfare.

Though the cause-and-effect aspect of this argument might seem hard to prove in court, global-warming victims in other corners of the country started filing similar lawsuits. In Comer v. Murphy Oil, residents of Mississippi’s Gulf Coast sued nearby oil refineries for damages they suffered during Hurricane Katrina, alleging that the refineries’ greenhouse-gas emissions contributed to the force of the storm. In 2008, in Native Village of Kivalina v. Exxon, residents of a small village on a barrier island off the Alaskan coast, whose homes are being steadily submerged by rising sea levels, filed suit against two dozen energy companies for their contribution to climate change. The villagers, who are native Inupiat, seek more than $400 million in damages to cover the cost of relocating their homes, again using the doctrine of nuisance law.

Each of these cases was dismissed at the trial court level. The judges said that the suits raised a “political question” not fit for the judicial branch to rule on-a tool that allows judges to punt tricky cases they don’t want to decide. Two of the lower courts also said that the parties lacked legal standing to bring the lawsuits, because they could not show their injuries were sufficiently traceable to the defendants’ conduct. However, the plaintiffs appealed these dismissals to federal courts of appeals, arguing that they do have standing and that the “political question” doctrine does not apply.

Then, to the shock of the legal community and even some environmentalists, two federal appeals courts reversed these rulings. Last September, after more than three years of deliberating, a two-judge panel on the U.S. Court of Appeals for the 2nd Circuit overturned the dismissal of Connecticut v. AEP in a sweeping 139-page opinion. A few days later, a three-judge panel of the U.S. Court of Appeals for the 5th Circuit released a similar opinion reinstating the Katrina victims’ lawsuit. The five judges responsible for these rulings-three of whom were appointed by Republican presidents-found that the plaintiffs had standing and that the evidence of the relationship between greenhouse gases and climate change was sufficient for the cases to go forward. The courts did not punt because of the “political question” doctrine, pointing out that federal courts have successfully handled public nuisance claims involving environmental damage for more than a century.

Following last Friday’s announcement that Justice John Paul Stevens will retire from the Supreme Court at the end of this term, President Obama hailed the Court’s most senior Justice as “an impartial guardian of the law.” This description is certainly accurate, and is perhaps best illustrated by Justice Stevens’ numerous rulings in environmental cases.

First, it is worth remembering that Justice Stevens came to the Court in 1975, at the dawn of the modern environmental movement and amid a heady time for environmentalists in the courts. Just a few years earlier, in a dissent from the landmark case Sierra Club v. Morton (1972), Stevens’ predecessor, Justice William O. Douglas, had famously argued that natural resources such as trees and rivers should have “standing,” positing that if corporations are permitted to represent their interests in court then so too should other inanimate objects. Meanwhile, in cases of statutory interpretation, judges on the powerful U.S. Court of Appeals for the D.C. Circuit had developed a number of doctrines that allowed them to aggressively second-guess agency decision-making in order to realize the broad and ambitious goals of environmental statutes. These developments invigorated environmentalists, but they also introduced a sense of permissive creativity into a rapidly growing body of environmental law, and exposed judges who made pro-environmental rulings to allegations of judicial activism.

Justice Stevens, by contrast, firmly rejected the idea that environmentalism was some sort of transcendental force that gave judges special powers to enforce broad statutory goals on their own and overrule regulatory agencies. Most famously, in Chevron v. NRDC (1984), he wrote a majority opinion for the Court that sternly rebuked the D.C. Circuit for substituting its judgment for that of the Reagan EPA, which had sought to give industry more flexibility in meeting their Clean Air Act obligations. Though a bitter defeat for environmentalists, Chevron, which holds that judges must defer to agencies when they make a reasonable judgment about an ambiguous law, is rightly hailed today as a landmark of both administrative law and judicial restraint.

Those same principles — deference to the plain language of statutes and concern about judicial restraint — are the hallmarks of Justice Stevens’ other landmark environmental rulings, which have rightly earned Stevens the enduring gratitude of the environmental world. In Babbitt v. Sweet Home Chapter Of Communities For A Great Oregon (1995), Justice Stevens wrote for a six -Justice majority in reinstating the portion of the Endangered Species Act that protects endangered species’ habitats, which had been struck down by the D.C. Circuit (which by then had been taken over by Reagan and Bush appointees). This time, Justice Stevens’ opinion corrected the D.C. Circuit’s narrow reading of an environmental statute by finding that the language and intent of the Endangered Species Act was clear in forbidding changes to habitats that will harm endangered species.

In 2002, Justice Stevens wrote another rule-of-law environmental opinion in Sierra Preservation Council v. Tahoe Regional Planning Agency, a “takings” case that followed a 15-year period during which the Court’s conservatives, led by Justice Scalia, had been remarkably inventive in trying to transform the Takings Clause of the Fifth Amendment into a barrier to environmental laws. Rejecting this bending of the Constitution’s meaning, Justice Stevens garnered another six-Justice majority in upholding land-use protections put in place to save Lake Tahoe. The ruling returned the Takings Clause to its more limited role as a guard for securing compensation for landowners when the government exercises its power of eminent domain.

Finally, and perhaps most famously, in Massachusetts v. EPA (2007), Justice Stevens relied on Chevron and the unambiguously broad terms of the Clean Air Act in holding that the EPA may regulate greenhouse gas pollution using its existing authority under the Act. This ruling has allowed the Obama Administration to aggressively combat global warming without waiting for further action by Congress, setting into motion a chain of regulatory actions that has led to the nation’s very first nationwide auto emissions standards aimed at greenhouse gases, and may soon lead to the nation’s first restrictions on CO2 emissions from power plants.

Justice Stevens should be remembered as a great justice in environmental cases, not because he bent the law to favor environmental outcomes, but rather because he insisted that the law itself, which dictates environmental outcomes in many cases, be followed.