Mayer Brown has one of the deepest benches in the appeals business. From January 2012 through the first quarter of this year, 27 firm lawyers argued appeals, handling 59 cases before 24 federal and state appellate courts. "We have lots of people contributing," said Evan Tager, co-chairman of the appellate practice. "We’re not focused on one or two people with all of the cases being theirs."

When two competitors of Arkema Inc. challenged the company’s trading of allowances of ozone-depleting hydrocholorofluorocarbons (HCFCs) under an Environmental Protection Agency cap-and-trade scheme, the firm turned to Mayer for help. Honeywell International Inc. and E.I. du Pont de Nemours and Co. had sought to invalidate certain HCFC trades Arkema had made in advance of an EPA rule change that ended certain types of HCFC exchanges. Partner Dan Himmelfarb helped Arkema win a 2-1 U.S. Court of Appeals for the D.C. Circuit ruling in January.

Hungary’s MKB Bank sought Mayer’s help when a group of Holocaust survivors and their heirs filed an Alien Tort Statute suit against it and three other banks for allegedly confiscating the assets of Jews. A federal trial judge in Illinois had allowed the suit to proceed to discovery and trial, but Mayer’s Charles Rothfeld and colleagues persuaded the Seventh Circuit to intervene. That court ruled for MKB on jurisdictional grounds and ordered the case dismissed.

Mayer handled one of the most significant environmental cases to come before the U.S. Supreme Court last year. In Decker v. Northwest Environmental Defense Center, partner Tim Bishop convinced the justices to reverse a Ninth Circuit ruling that runoff from forest roads was subject to permitting under the Clean Water Act. The decision for Mayer’s timber industry clients came despite EPA’s effort to amend the regulations on the eve of oral argument last fall.

The firm has carved out a reputation for writing amicus briefs. Andrew Pincus contributed one such on behalf of a group of law professors who argued that the Affordable Care Act was constitutional because its mandate to purchase health insurance could be viewed as a tax — the very point Chief Justice John Roberts Jr. cited in upholding the law.

Regarding the Defense of Marriage Act, partner Miriam Nemetz filed an amicus brief on behalf of more than 200 members of Congress arguing that there was no "legitimate federal interest" for the government to deny recognition to same-sex marriages. That case, of course, remains pending. 

Correction: This article has been corrected to reflect that partner Miriam Nemetz argued there was no legitimate federal interest in denying recognition of same-sex marriages. We regret the error.