In the case of Boyce Motor Lines, Inc. v. United States in 1951, the U.S Supreme Court ruled on a matter concerning regulatory clarity and fair notice to those being regulated. The petitioner, Boyce Motor Lines, was charged with violating safety regulations issued by Interstate Commerce Commission (ICC) for operating its trucks in hazardous conditions without obtaining special permits or following prescribed routes as required by ICC rules. However, Boyce argued that these regulations were too vague and did not provide clear guidance on what constituted 'hazardous' conditions or how to comply with them effectively. The court held that while it is true that due process requires reasonable certainty in laws so individuals have adequate notice of prohibited conduct; this does not mean every regulation must be perfectly clear or free from possible misinterpretation. A statute is not unconstitutionally vague if its meaning can be objectively determined using common understanding and practices. Therefore, even though there might have been some ambiguity about what constitutes "hazardous" under ICC's rules; it would be unreasonable to expect perfect clarity given the complex nature of transportation safety issues involved here.

In the dissenting opinion for Boyce Motor Lines, Inc. v. United States, the justice argued that the Interstate Commerce Commission's regulation was too vague and therefore violated due process rights under the Fifth Amendment of the Constitution. The regulation in question required truck drivers to avoid congested areas or places where crowds were assembled when it was "practicable" to do so. However, what constituted as "practicable" wasn't clearly defined by law or regulations which left room for arbitrary enforcement and interpretation by officers on duty at any given time. This lack of clarity could potentially lead to unfair punishment for those who might not have a clear understanding of what is expected from them under this rule - thus violating their right to fair notice about prohibited conduct.