Why was cultural burning banned in California?

Short answer

The Karuk Tribe records the reason without hedging, that California's laws intended to outlaw various forms of Indigenous burning and penalized tribal communities for using fire as a ceremonial and natural resource management tool. Those restrictions disrupted Traditional Ecological Knowledge, practice, and belief systems. The first ban came in 1850, inside legislation designed to force Indigenous people off their ancestral lands. A second ban in the 1930s ended broadcast burning by the settlers who later ranched the same ground.