## Facts

- Boyce Motor Lines, an interstate motor carrier, transported carbon bisulphide, an inflammable liquid.
- Federal law authorized criminal penalties for knowingly violating ICC safety regulations governing transportation of dangerous materials.
- An ICC regulation required drivers transporting specified hazardous materials to avoid, so far as practicable, driving into or through congested thoroughfares and certain structures, including tunnels.
- The indictment alleged that on three occasions Boyce routed a truck carrying carbon bisulphide through the Holland Tunnel between Cascade Mills, New York, and Brooklyn, New York, despite other available and more practicable routes.
- On the third trip, the cargo exploded in the tunnel, injuring about sixty persons.
- The indictment alleged Boyce knew the tunnel route violated the ICC regulation; it did not charge any failure to prearrange routes.

## Issues

1. Whether the ICC regulation’s requirement to avoid, “so far as practicable,” driving through “congested thoroughfares” (including tunnels) was unconstitutionally vague under due process when enforced criminally through a “knowingly violates” statute.
2. Whether the district court properly dismissed the indictment counts on vagueness grounds.

## Decision

- The Supreme Court affirmed the court of appeals and reinstated the dismissed counts.
- The Court held the regulation was not void for vagueness as applied to the charged conduct.
- The Court reasoned the regulation provided a reasonably certain standard when combined with the statutory requirement that the violation be knowing.
- For conviction, the government must prove not only that a commercially practicable and appreciably safer alternative route existed, but also that the carrier knew of it and deliberately chose the more dangerous route, or willfully failed to inquire.

## Legal Principles

- Due process requires criminal prohibitions to be sufficiently definite to give notice to those seeking to avoid penalties and to guide adjudication and defense.
- Absolute precision is not required; many prohibitions must address varied factual situations, so only a reasonable degree of certainty is demanded.
- A scienter requirement can reduce vagueness concerns by limiting liability to those who knowingly (or willfully blindly) engage in proscribed conduct near the line of illegality.
- A “so far as practicable” standard in a safety regulation may be constitutionally enforceable where guilt depends on proof of knowledge and the availability of a safer, practicable alternative.

## Conclusion

The Court upheld criminal enforcement of the ICC hazardous-materials routing rule, concluding that the “so far as practicable” standard, coupled with a requirement of knowing violation and proof of a known safer practical alternative, provided constitutionally adequate notice and restraint on prosecutorial and judicial discretion.


Boyce Motor Lines, Inc. v. United States, 342 U.S. 337 (1952)