Baddour ruled the law against "indecent or profane language" within earshot of two or more people on any public road in North Carolina is too broad.
"There is no longer any consensus, if there ever was, on what words in the modern American lexicon are 'indecent' or 'profane,"' Baddour wrote. "A reasonable person cannot be certain before she acts that her language is not violative of this law, and it is therefore unconstitutionally vague."
The case started Feb. 15 when Elabanjo was having a conversation on Franklin Street in Chapel Hill, and stepped into the road as a police cruiser drove by, according to court documents. The two officers asked her to get back on the sidewalk. She did, but told the officers "You need to clean up your damn, dirty car" while still in the road.
After she was back on the sidewalk, Elabanjo waved her arms and called the officers a vulgar name. They arrested her, charging her with disorderly conduct and use of profanity on a public road.
At July trial, a judge dismissed the disorderly conduct charge but found Elabanjo guilty of using profanity. The vulgar term wasn't at issue, because she uttered the word while standing on the sidewalk.
The law, adopted in 1913, made profanity spoken in a "loud and boisterous" manner a crime in all North Carolina except Pitt and Swain counties. It wasn't cear why those counties were deemed free zones for salty language.
Raleigh lawyer Matthew Quinn, who represented Elabanjo in her appeal, said the judge's ruling is a victory for free speech.
"It's not an easy thing to find a statute unconstitutional," he said. "It's a big deal. It's a testament to the First Amendment and to our judicial system."
Elabanjo appealed her conviction with the help of the state chapter of the American Civil Liberties Union, which hailed Baddour's ruling.
Calls to the office of District Attorney Jim Woodall, who oversees Orange and Chatham counties, were not returned late Friday.