Three young boys in Colorado learned a harsh lesson in business and regulation over Memorial Day weekend.

Jennifer Knowles, the boys’ mother, encouraged her three sons to open a lemonade stand across the street from their house in the Denver suburb of Stapleton, Colorado, FOX 4 reported.

“I want to teach my kids about being an entrepreneur and having your own business. My 6-year-old got his little toy cash register out that he got when he was about 2 or 3 and he was learning how to interact with customers and about customer service.”

But within a half hour of the boys setting up their stand, police arrived inquiring about a permit.

“The police officers came over and they said that because my boys and I did not have permits for a lemonade stand they shut us down and we had to stop immediately,” Knowles said.

According to Knowles, a neighbor had complained to police. Knowles said the boys, ages 4 to 6, were planning to donate the proceeds to Compassion International, a charity group.

Communications Program Manager Alexandra Foster said permit laws for businesses run by minors are not usually enforced, but police will respond if a complaint is made.

“If our inspectors go to a lemonade stand, it means we’ve received a complaint, and generally complaints stem from high levels of activity or noise that disrupts neighbors,” Foster said.

By contrast, neighboring Utah passed SB 81, a bipartisan bill that exempts minors who operate a business from obtaining a permit.