The Moomins (1978)

S1E43 Midsummer Night

Moomin and the Snork Maiden make their way to Fillyjonk's home, where they join forces to organize the midsummer night celebration. As they gather firewood, they stumble upon the prohibition signs that Snufkin had hidden away from Hemulpark. Unfortunately, the park ranger mistakenly identifies them as troublemakers and ends up imprisoning the trio.