TOBIAS LOSS-EATON is an appellate and regulatory litigator who helps clients navigate complex, novel, or high-stakes legal issues, from the earliest strategy discussions to the U.S. Supreme Court. Chambers USA, which has ranked him for Transport: Rail (for Railroads) in USA—Nationwide (2023–2025), notes his “impressive experience,” with clients reporting that he is “a fantastic lawyer” and “an excellent civil litigation advocate” who “provides great client service.” One client tells Chambers: “Tobias is my first call when there is no playbook for complex issues. He approaches issues with calm, reasoned discernment. His judgment, intellect and writing abilities are top-rate.”
As a member of Sidley’s Supreme Court & Appellate and Regulatory Litigation practices, Tobias has extensive experience challenging and defending state and federal agency actions and regulations, including in the environmental, trade, securities, and healthcare sectors. That experience includes addressing the key threshold questions of when, where, and how to press an issue in the proper judicial forum—including issues of personal jurisdiction, sovereign immunity, federal removal jurisdiction, and abstention. It also includes substantial experience with federal preemption and Takings Clause issues. Tobias also has significant experience in complex contractual and commercial disputes, including cases involving the Federal Arbitration Act and insurance and reinsurance issues.
Tobias is also part of Sidley’s top-ranked Transportation group. Chambers USA highlights his strong experience advising and litigating on behalf of the nation’s largest freight railroads (2023 and 2024). He has represented the railroads in many cases involving federal preemption or preclusion, contractual disputes, challenges to regulatory action, and the proper interpretation of the Federal Employers Liability Act (FELA). He also advises and litigates on behalf of airline-industry clients on preemption and regulatory issues. In 2023 alone, Tobias argued four transportation-law appeals in federal and state appellate courts.
Tobias prides himself on clearly explaining complex legal issues to busy generalist judges. One prominent legal writing expert has praised Tobias’s briefs as better than the typical work product of “elite” Supreme Court advocates. Tobias has written or coauthored over 180 briefs in state and federal appellate courts, including 88 briefs in the Supreme Court. He has presented oral argument in the Second, Fourth, Sixth, Seventh, and D.C. Circuits and in state appellate and supreme courts, producing successful results for his clients in 70% of the appeals he has argued.
Tobias is a co-director of the Northwestern Supreme Court Clinic at Northwestern Pritzker School of Law, where he teaches Supreme Court advocacy, moots advocates preparing for merits arguments, and supervises students working with Sidley lawyers on cases at the Court.
Tobias’s recent Supreme Court cases include:
- Securing a contested vacatur and remand in Fields v. Colorado, No. 24-5460 (2025), addressing the Sixth Amendment’s application to state habitual-offender regimes.
- Representing the petitioner in Brown v. United States, 144 S. Ct. 1195 (2024), a merits case addressing the meaning of “serious drug offense” under the Armed Career Criminal Act.
- Representing the respondent in Mallory v. Norfolk Southern Railway, 600 U.S. 122 (2023), a major merits case addressing whether a state can assert general personal jurisdiction over any foreign corporation registered to do business there.
- Representing the petitioner at the certiorari stage and on the merits in Kahler v. Kansas, 140 S. Ct. 1021 (2020), a landmark case addressing whether the Constitution requires an insanity defense.
- Representing the respondents at the merits stage in United States v. Davis, 139 S. Ct. 2319 (2019), a successful due process challenge to a federal gun-possession statute.
His other significant matters include:
- Successfully briefing and arguing a Virginia Supreme Court appeal challenging a law conferring eminent-domain power on private broadband cable companies under the Virginia Constitution’s takings clause.
- Representing a national business federation as amicus supporting an airline-industry challenge to a Department of Transportation regulation about ancillary fees, whose specific arguments the Fifth Circuit adopted in staying the regulation.
- Successfully briefing and arguing a Sixth Circuit appeal to secure a ruling that the ICC Termination Act preempted a state-law property claim aimed at a railroad right-of-way, overturning an adverse district court ruling.
- Securing in district court—and then successfully briefing and arguing a Fourth Circuit appeal to defend—a multi-million-dollar breach-of-contract judgment arising from a rent-determination process under a long-term fiber-duct lease.
- Securing in district court—and then successfully briefing and arguing a Second Circuit appeal to defend— dismissal of “fraud on the FDA” claims against a pharmaceutical manufacturer under the False Claims Act.
- Successfully briefing and arguing a Seventh Circuit challenge to a Surface Transportation Board decision construing common-carrier railroads’ interchange obligations.
- Representing a national industry association in successfully challenging a customs regulation restricting excise-tax exemptions in the Court of International Trade, one of Law360’s top five trade rulings of 2020, and successfully defending the decision on appeal in the Federal Circuit.
- Briefing and arguing a D.C. Circuit challenge to a regulation requiring railroads to disclose information about hazardous materials movements without confidentiality protections.
- Representing a natural gas company in Second Circuit and New York appellate cases about environmental approvals and eminent domain proceedings, including a successful challenge to a state agency’s denial of a Clean Water Act certification, which earned Law360’s “Legal Lion of the Week” title, and a successful defense of FERC’s subsequent waiver ruling.
Before joining Sidley’s D.C. office, Tobias served as a law clerk to Judge Norman H. Stahl of the U.S. Court of Appeals for the First Circuit and Judge Henry H. Kennedy, Jr. of the U.S. District Court for the District of Columbia. Between his clerkships, he was an associate in Sidley’s New York office, where he focused on commercial litigation and disputes.
Tobias earned his J.D., cum laude, from Harvard Law School, where he was a senior policy editor of the Harvard Law & Policy Review and notes editor of the Harvard Law Review.