Alabama Dept. of Revenue v. CSX Transp., Inc., 575 U.S. 21

Background

Alabama applies a 4% sales-and-use tax to diesel fuel purchases for rail operations but exempts motor carriers and water carriers; motor carriers instead pay a 19¢/gallon fuel-excise tax, while water carriers pay neither tax. Parties stipulated that rail, motor, and water carriers compete.
CSX (rail carrier) sued under 49 U.S.C. §11501(b)(4) (the 4–R Act), seeking to enjoin collection of sales tax on its diesel purchases as discriminatory against rail carriers.
On first appeal this Court reversed a dismissal, holding §11501(b)(4) prohibits taxation that treats “groups [that] are similarly situated” differently without adequate justification (CSX I). The case returned after trial.
The Eleventh Circuit held competitors were an appropriate comparison class but refused to consider Alabama’s contention that the motor‑fuel excise tax justified the motor carrier sales‑tax exemption.
The Supreme Court (majority) held competitors can be a valid comparison class when the alleged discrimination is between modes of transport and remanded for the Eleventh Circuit to consider whether Alabama’s alternative taxes (notably the motor‑fuel excise) justify the differential treatment; the majority left any state justifications for water‑carrier exemption for remand.

Issues

Issue	Plaintiff's Argument (CSX)	Defendant's Argument (Alabama)	Held
Appropriate comparison class under §11501(b)(4)	Competitors (motor and water carriers) are the right class because the tax disadvantages rail carriers relative to their transport competitors.	The comparison class must be general commercial and industrial taxpayers (the class referenced in subsections (b)(1)–(3)).	Competitors may be an appropriate comparison class when the claimed discrimination is vis‑à‑vis competitors; comparison class depends on the theory of discrimination alleged, but must consist of "similarly situated" persons.
Whether exemption for motor carriers is justified by an alternative tax (fuel‑excise)	Sales‑tax discrimination exists even if competitors pay a different tax; the focus should be the challenged tax alone.	The motor‑fuel excise tax on motor carriers (but not railroads) may justify exempting motor carriers from the sales tax; courts may consider other taxes in the State’s overall scheme.	State may justify a differential sales‑tax treatment if competitors pay a roughly equivalent alternative tax; remand to evaluate whether Alabama’s fuel‑excise tax is the rough equivalent.
Water‑carrier exemption: is it permissible?	Water carriers’ exemption shows discriminatory treatment of railroads.	Water carriers are exempt for independent reasons (e.g., federal law or other rationales).	The State cannot defend the water‑carrier exemption by pointing to the motor‑fuel excise; the Eleventh Circuit should examine Alabama’s alternative rationales on remand.

Key Cases Cited

CSX Transp., Inc. v. Alabama Dept. of Revenue, 562 U.S. 277 (2011) (held §11501(b)(4) prohibits treating "groups [that] are similarly situated" differently without sufficient justification)
Gregg Dyeing Co. v. Query, 286 U.S. 472 (1932) (negative Commerce Clause precedent allowing consideration of taxes on third parties as justification)
New York Rapid Transit Corp. v. City of New York, 303 U.S. 573 (1938) (discussing permissible tax distinctions among utilities and other businesses)
Department of Revenue of Oregon v. ACF Industries, Inc., 510 U.S. 332 (1994) (emphasizing need for clarity when limiting state taxation authority)