Bibb, Director, Dept. of Public Safety of Illinois v. Navajo Freight Lines, Inc.

359 U.S. 520 (1959)

Quick Summary

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Bibb (defendant) enforced an Illinois law requiring curved mudguards on trucks, which Navajo Freight Lines, Inc. (plaintiff), an interstate trucking company, challenged as overly burdensome to interstate commerce. The Illinois regulation conflicted with other states’ laws, particularly Arkansas’s requirement for straight mudguards.

The Supreme Court had to decide if this state law unduly impeded the free flow of interstate commerce. The Court affirmed the lower court’s ruling, concluding that the Illinois statute placed an unconstitutional burden on interstate commerce due to its conflict with other states’ regulations and its negative impact on trucking operations.

Facts of the Case

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Illinois enacted a law that mandated commercial trucks to install curved mudguards on their rear wheels. Conversely, Arkansas and other states mandated straight mudguards for trucks traversing their territories.

Navajo Freight Lines, Inc. (plaintiff), an interstate trucking company, challenged the Illinois requirement enforced by the Director of Public Safety of Illinois, Bibb (defendant), as unconstitutional. The plaintiff contended that the need to change mudguards to comply with varying state laws placed an excessive burden on interstate commerce.

The dispute originated when the plaintiff faced conflicting state regulations that impeded its trucking operations across state lines. The Illinois law required a specific type of mudguard that did not align with the specifications required in Arkansas and other states, leading to operational challenges and legal contention.

Procedural Posture and History

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  1. The plaintiff brought suit in district court claiming the Illinois law was an unconstitutional burden on interstate commerce.
  2. The district court agreed with the plaintiff and declared the Illinois law unconstitutional.
  3. The defendant, Bibb, appealed the district court’s decision to the United States Supreme Court.

I.R.A.C. Format


Issue Icon

Whether the Illinois law mandating curved mudguards on commercial trucks constitutes an unconstitutional burden on interstate commerce.

Rule of Law

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State regulations must not conflict with the Commerce Clause of the Constitution, which aims to maintain free trade among states. While safety measures generally carry a presumption of validity, they must not impose an undue burden on interstate commerce.

Reasoning and Analysis

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The Supreme Court recognized that while states have broad authority to regulate highway safety, such regulations must not place an excessive burden on interstate commerce. In this case, the conflicting requirements between Illinois and other states like Arkansas forced trucking companies to change their equipment according to differing local laws, causing significant delays and increased costs.

The Court also considered the negative impact on ‘interline’ operations where trailers are interchanged between carriers without unloading and reloading cargo. The Illinois law complicated this efficient system, particularly for perishable goods or hazardous materials like explosives.

The Court ultimately found that the benefits claimed by Illinois for its unique mudguard design were not substantial enough to override the significant burdens imposed on interstate commerce.


Conclusion Icon

The Supreme Court affirmed the lower court’s decision, holding that the Illinois statute was an unconstitutional interference with interstate commerce.

Concurring Opinions

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Justice Harlan, joined by Justice Stewart, concurred with the judgment, noting that the District Court’s findings demonstrated no safety advantages of the Illinois-required contour mudflap over conventional flaps. Therefore, the burden on interstate commerce was unjustifiable.

Key Takeaways

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  1. State regulations related to highway safety are subject to scrutiny under the Commerce Clause when they present a significant burden to interstate commerce.
  2. A state cannot enforce a safety regulation that significantly disrupts the operations of interstate carriers if it conflicts with regulations of other states.
  3. The efficiency of ‘interline’ trucking operations is an important consideration in evaluating the impact of state regulations on interstate commerce.

Relevant FAQs of this case

What constitutes an undue burden on interstate commerce under the Commerce Clause?

An undue burden on interstate commerce arises when a state’s regulatory measure is excessively restrictive or inconsistent with measures in other states, leading to significant disruptions in the free flow of trade and services across state lines. It occurs when the burden on interstate commerce outweighs the local benefits purportedly sought by the state regulation.

  • For example: A state’s law that requires vehicles to use a specialized fuel not widely available outside its borders would impede the normal flow of transportation services across states, constituting an undue burden.

How do courts balance state police powers with the federal interest in facilitating interstate commerce?

Courts balance state police powers and the federal interest by employing a form of judicial scrutiny where state laws are evaluated to ensure they serve a legitimate local public interest, like safety or health, and are not simply protectionist measures. Such laws must also not excessively interfere with interstate commerce.

  • For example: A state may impose safety regulations for products entering its market, but if these regulations significantly differ from national standards to the point of hindering producers from other states to compete fairly, courts may rule them as overly burdensome to interstate commerce.

Is the presence of conflicting state regulations enough to prove an unconstitutional burden on interstate commerce?

Conflicting state regulations alone are not enough to prove an unconstitutional burden. Courts must assess the actual impact of these regulations on interstate activities. A regulation only becomes burdensome if it creates significant operational challenges or costs for businesses operating across state lines.

  • For example: If a truck manufacturer has to produce multiple models of a vehicle to meet various emission standards in different states, resulting in increased costs and complexity in production, this scenario could be seen as burdening interstate commerce.


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