A small town in Massachusetts has essentially started a public swear jar for its residents.

Residents of Middleborough, Mass., tired of hearing profanity in public, reappropriated a parental tool to curb cursing and voted to institute a $20 fine for anyone heard letting obscenities fly in public.

The town of 20,000 already had a bylaw against cursing, but authorities rarely enforce such an ordinance as obscenities are so common in modern conversation.

The problem with the fine is obscenities, while unpleasant, are constitutionally protected speech. So the town’s new fine is butting heads with federal law, which could spell trouble down the road should a resident be fined and challenge the bylaw in court.