Using the National Trails System Act, the federal Surface Transportation Board (STB) sought to convert a strip of abandoned railroad tracks in Oregon into a recreational trail—part of a nationwide “rails-to-trails” project. The STB misinterpreted the state’s property laws, however, under which the abandoned property interest is an easement that was granted to the railroad over a century ago for the sole purpose of operating a railroad. After the railroad ceased operating, the easement was abandoned, and the strip of land is supposed to return to the owner of the land traversed by the easement.

The STB’s bad interpretation of property law drew rightful protest from scores of current owners. Those owners argue that converting the abandoned rail line to a recreational trail is a taking of their property, meaning they are owed compensation under the Fifth Amendment. But the Federal Circuit ruled against them, even though the owners’ argument relied on a question of state law that the Oregon Supreme Court has not yet ruled on.

The Cato Institute, joined by the National Association of Reversionary Property Owners, the Reason Foundation, Southeastern Legal Foundation, and Professor Shelley Ross Saxer, have filed an amicus brief in support of the owners, urging the Supreme Court to rule that, under longstanding principles of federalism, it is up to the states’ courts—not the federal judiciary—to interpret their own laws. While federal courts often rule on issues of state law, it is abnormal for them to do so without first asking a state’s highest court to determine an issue of state law that is unresolved. Here, the Federal Circuit more or less guessed how the Oregon Supreme Court would rule, and it was probably bad guess based on Oregon precedents.

Under the prevailing view of federalism, a federal court cannot presume, independently, to declare state law. That’s a job for the state’s highest court, which is the supreme authority in all matters of state law that do not contradict federal law or the Constitution. Federal courts can certify questions of state law to a state’s highest court, and this happens quite often.

The Federal Circuit’s choice to make guesswork of Oregon law threatens the delicate jurisdictional balance between the federal government and the states. States have the final say on their own laws for good reason. First, it promises greater interpretive accuracy. Who better to decide questions of a particular state’s laws than those courts most versed in them? Second, it prevents the federal courts from interpreting state laws in ways that unduly favor federal agencies—a process that could gradually sap state-court precedents of any relevance in cases brought at the federal level. The Supreme Court should take this case to make clear to the Federal Circuit that the tenets of federalism are to be taken seriously.