Justice Brennan, joined by Justice Marshall, maintained that the ordinance was content based on its face. It imposed special location limits exclusively on theaters showing adult films while leaving ordinary theaters and other adult businesses, such as bars and bookstores, unregulated. A secondary-effects rationale may supply a reason to regulate, he argued, but it does not erase the ordinance's content-based classification.
In his view, the ordinance's underinclusiveness was especially revealing. Renton had not explained why adult theaters, but not other businesses with assertedly similar secondary effects, warranted regulation. The ordinary rule allowing legislatures to address problems one step at a time has less force when the classification turns on the subject matter of protected expression.
Justice Brennan also found Renton's claimed secondary-effects purpose inadequately supported. The City Council conducted no local studies, heard no expert testimony, and preserved no evidence showing how a theater would harm the particular schools, churches, parks, or residences covered by the ordinance. The post-litigation amendment reciting findings about secondary effects appeared, in his view, to be a conclusory and suspiciously timed effort to justify the restriction.
Renton's general reliance on Seattle and Detroit did not cure that evidentiary gap. Those cities had studied different conditions and adopted different regulatory solutions; their experience did not establish that Renton's particular 1,000-foot restrictions were necessary for Renton's particular problems. A content-based law therefore could not survive strict scrutiny because Renton had not shown that it was precisely drawn to serve a compelling interest.
Even if analyzed as content neutral, Justice Brennan concluded, the ordinance failed intermediate scrutiny. The city had not sufficiently substantiated a significant interest, and the supposed 520 acres of available land included occupied or unsuitable sites. By confining theaters to areas that were largely unavailable or impractical, the ordinance could effectively deprive speakers of a reasonable opportunity to exhibit constitutionally protected films.