Southern Pacific Co. v. Arizona,
325 U.S. 761 (1945)

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U.S. Supreme Court

Southern Pacific Co. v. Arizona, 325 U.S. 761 (1945)

Southern Pacific Co. v. Arizona

No. 56

Argued March 26, 27, 1945

Decided June 18, 1945

325 U.S. 761


1. State power to regulate the length of railroad trains is not curtailed or superseded by § 1 of the Interstate Commerce Act (paragraphs 117) of itself, and in the absence of administrative implementation by the Interstate Commerce Commission; nor by provisions of the Safety Appliance Act for brakes on trains; nor by the provision of § 25 of Part I of the Interstate Commerce Act permitting the Commission to order the installation of train stop and control devices. Pp. 325 U. S. 765-766.

In enacting legislation within its constitutional authority over interstate commerce, Congress will not be deemed to have intended to strike down a state statute designed to protect the health and safety of the public unless its purpose to do so is clearly manifested, or unless the state law, in terms or in its practical administration,

Page 325 U. S. 762

conflicts with the Act of Congress or plainly and palpably infringes its policy. P. 325 U. S. 766.

2. The Arizona Train Limit Law (Arizona Code Ann., 1939, § 69-119), making it unlawful to operate within the State a passenger train of more than fourteen cars or a freight train of more than seventy cars, held, as applied to interstate trains, invalid as contravening the commerce clause of the Federal Constitution. Pp. 325 U. S. 763, 325 U. S. 781.

3. The commerce clause, even without the aid of Congressional legislation, protects against state legislation which is inimical to the national commerce, and in such cases, where Congress has not acted, this Court, and not the state legislature, is the final arbiter of the competing demands of state and national interests. P. 325 U. S. 769.

4. Although this Court, upon review of a decision of a state court, may determine for itself the facts upon which an asserted federal right depends, the crucial findings of the state court here are not challenged in material particulars, are supported by evidence, and supply an adequate basis for decision of the constitutional issue presented. P. 325 U. S. 771.

5. The state regulation here involved, admittedly obstructive to interstate train operation, and having a seriously adverse effect on transportation efficiency and economy, passes beyond what is plainly essential for safety, since it does not appear that it will lessen, rather than increase, the danger of accident. Examination of all relevant factors makes it plain that the state interest here asserted is outweighed by the interest of the nation in an adequate, economical and efficient railway transportation service. P. 325 U. S. 781.

6. The relative weights of the state and national interests involved are not such as to make inapplicable the rule, generally observed, that the free flow of interstate commerce and its freedom from local restraints in matters requiring uniformity of regulation are interests safeguarded by the commerce clause from state interference. Pp. 325 U. S. 770, 325 U. S. 781.

7. The "full train crew" cases and South Carolina Highway Dept. v. Barnwell Bros., 303 U. S. 177, distinguished. P. 325 U. S. 782.

61 Ariz. 66, 145 P.2d 530, reversed.

APPEAL from a judgment upholding the constitutionality of the Arizona Train Limit Law.

Page 325 U. S. 763

Primary Holding

A Commerce Clause analysis is based on balancing the nature and extent of the burden on interstate commerce created by the state law against the benefits and objectives of the law.


Arizona imposed a monetary penalty on railroad companies that operated trains within the state of more than 14 passenger cars or 70 freight cars. It sought to recover these penalties from Southern Pacific Co., but the trial court made detailed factual findings that led it to conclude that Southern Pacific was not liable because the law violated the Commerce Clause. The Arizona Supreme Court reversed on the grounds that the law was reasonably related to the health and safety of the state's citizens and that the state had properly based it on its police power. It held that this foundation insulated it from challenges under the Commerce Clause, even though it had an adverse effect on interstate commerce.



  • Harlan Fiske Stone (Author)
  • Owen Josephus Roberts
  • Stanley Forman Reed
  • Felix Frankfurter
  • Frank Murphy
  • Robert Houghwout Jackson

The states cannot substantially impede interstate commerce or undermine national uniformity in areas that require it, even in exercising their authority over local matters. Most major U.S. railroad companies operate trains of lengths longer than those permitted by this law. As a result, national uniformity for the regulations in this area is virtually essential for the interstate railway system to operate properly. The law has an impact on railroad operations that extends well beyond the state because it requires companies to break up and reassemble longer trains.

Safety does not provide a reasonable basis for this law because increasing the number of trains increases rather than decreases the number of accidents. The law was meant to reduce slack action accidents, which are more common among longer trains. The trial court noted, though, that these accidents are no less common in Arizona than in neighboring Nevada, where there is no such regulation. Any slight effect in improving railroad safety thus cannot outweigh the significant federal interest in protecting the flow of interstate commerce from interference by states.


  • Wiley Blount Rutledge (Author)


  • Hugo Lafayette Black (Author)


  • William Orville Douglas (Author)

Case Commentary

If the private actor can demonstrate effects outside the state by a state economic regulation, the state must show that the regulation has more benefits than it has burdens. This shifting of the burden of proof can be a crucial factor in Dormant Commerce Clause cases.

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