Sidley Austin likes to brag that it was the first law firm to establish a stand-alone U.S. Supreme Court appellate practice—back in 1985. It’s kind of like a middle-aged man reliving his high school football days, except that in Sidley’s case, the boast still carries a lot of weight.

That’s because Sidley is consistently involved—directly or indirectly through ami­cus filings—in approximately 40 percent of the cases the Supreme Court hears each term. Since the firm founded its Supreme Court practice more than 25 years ago, its lawyers have argued 106 high court cases. In the 2010 term, they argued six and briefed three more on the merits. Included in its recent Supreme Court wins is one of the most important global warming cases to date, American Electric Power v. Connecticut . Sidley’s victory for utilities in that matter staved off what could have been an onslaught of lawsuits against industries seeking to limit greenhouse gas emissions under federal common law.

But it’s not just its Supreme Court docket that lands Sidley on our finalist list for the first time. It also notched trial court–level victories for Tyson Foods, Inc., in-flight Internet connector Aircell, and power converter manufacturer SynQor, Inc. On an appeal, it secured a $200 million award for Vivendi and its Argentine subsidiary in a decades-long water service dispute. And on behalf of Airbus S.A.S., it defeated a signifiant portion of claims brought by the United States against the French aircraft maker and the European Union in the World Trade Organization.

Much of the credit for the firm’s Supreme Court work lands squarely on the shoulders of Carter Phillips, the managing partner of the firm’s Washington, D.C., office. As of mid-December, Phillips had argued 73 cases before the Supreme Court, more than any other lawyer in private practice.

Last May, Phillips appeared before the Supreme Court on behalf of General Dynamics Corporation and The Boeing Company, trying to reverse a $3 billion award levied against the companies in a long-standing battle with the U.S. government. The dispute stemmed from a contract that the U.S. Department of Defense canceled in 1988. The U.S. Court of Appeals for the Federal Circuit had allowed the government to invoke the state secrets privilege to keep classified certain contract information, which prevented the companies from using that information in their defense. The justices overturned that decision and the multibillion-dollar award 9 to 0, ruling that the government cannot hide behind the state secret clause if the information is vital to the payment claim.

“Carter cuts to the core of every case,” says Neal Katyal, who represented the U.S. in that case as acting solicitor general. “When asked a question by a justice, he generally has just one answer, whereas some lawyers have five.” Last year Phillips also secured a 7-to-2 Supreme Court victory for CSX Transportation, Inc., that allowed the rail company to challenge taxes imposed on it by the state of Alabama.

In the much-watched global warming case of AEP v. Connecticut , Phillips played a supporting role, with partner Peter Keisler taking the lead in diffusing what could have been a major blow to industries everywhere. The attorneys general of eight states, including Connecticut, and three land trusts filed the initial suit in 2004, claiming that the utility defendants’ carbon dioxide emissions created a public nuisance by contributing to global warming. The plaintiffs sought injunctive relief, asking the court to require the utilities to reduce their greenhouse gas emissions by an additional 2 percent each year for ten years.

The district court dismissed the case, deciding that global warning disputes should be resolved through legislation. Yet the U.S. Court of Appeals for the Second Circuit reversed, ruling that such issues were not reserved for the political sphere.

Had the Second Circuit’s decision been upheld, any emitter of greenhouse gases—from the smallest agricultural entity to the biggest industrial company—could have been the target of a global warming lawsuit under common law. Representing AEP, Xcel Energy Inc., Southern Company, Duke Energy, and the Tennessee Valley Authority, Keisler convinced the Supreme Court to rule last June that Congress and the Environmental Protection Agency, not the courts, should regulate greenhouse gases.

Sidley also flexed its appellate muscles on the international stage in a dueling World Trade Organization dispute between the United States and the European Union over each government’s financial support for Boeing and Airbus, respectively. In one of the more recent stages of this decades-long battle, Sidley helped convince the WTO’s appellate body to reject claims filed by the U.S. challenging E.U. subsidies provided to client Airbus. While the outcome is difficult to evaluate because the U.S. did prevail on some issues, Sidley asserts that it defeated 90 percent of the U.S.’s claims, including the most serious charge that Airbus received prohibited export subsidiaries.

In another major international matter, the firm won a $200 million arbitration award for Vivendi and its Argentine unit. The dispute stemmed from an Argentine province’s decision to renationalize water and sewage services that it had previously hired Vivendi to provide. In the course of trying to force Vivendi to renegotiate the terms of its contract, the provincial government convinced customers not to pay their water bills, which caused Vivendi to lose $2–3 million each month and to cancel the 30-year contract. A tribunal at the International Centre for Settlement of Investment Disputes determined that the province had breached its agreement and awarded Vivendi the $200 million.

Back in U.S. courtrooms, partner Thomas Rein won a patent infringement verdict for first-time client SynQor, Inc., which was awarded $95 million by a jury against 11 defendants. That amount was later increased to $110 million when Sidley sought supplemental damages and sanctions against two of the defendants for discovery abuses.

“Being able to converse with our president at a high technical level is impressive enough,” says SynQor general counsel Arthur Hofmann. But Sidley went a step further by translating that technical knowledge into court pleadings, he says.

In the past, Sidley has landed in our Honorable Mention pool. This year, the firm’s Supreme Court record, its solid trial results, and its comprehensive environmental work have catapulted it into our winners’ circle.

Now it’s got something new to brag about.

Department Size: Partners: 331, Associates: 408, Counsel: 82

Department as Percent of Firm: 50%

Percent of Firm Revenues: 50%