Chris Trumbull said Leviticus 20:13 inspired him to paint "To be gay = death" on a fence passed daily by students of nearby Roosevelt High School.
"I put it up because society is not looking at the truth," Trumbull told The Casper (Wyo.) Star-Tribune in a story published Tuesday.
Leviticus 20:13 reads, "If a man lies with a man as one lies with a woman, both of them have done what is detestable. They must be put to death; their blood will be on their own heads."
Trumbull's right to freedom of speech prohibits authorities from removing the message, city spokeswoman Shelley LeClere said.
Marty Wood, safe schools coordinator for the Natrona County School District, said teachers could use the issue to educate students about handling differences of opinion in a free country.
"I'd use it as a big learning piece about free speech and constitutional rights," Wood said.