Why are products labeled as 'known to the state of california to cause cancer' still sold in other states? Or are they sold in california, as well, so long as they're labeled?

Labeled to cause CA. The government requires some products to be labeled as such. Look at cigarettes. Known to cause cancer, heart disease, strokes, and birth defects...But still sold. Oh but labeled so now you are informed! it is just a legislative issue which may be different from state to state. Many products have been linked to cancer but not definitely known to cause it.
Likely diff. rules. This may be similar to the guidelines with cigarrettes. These are known to be dangerous to health but are sold in states anyway. They are labeled as such, yet people use them. Some products are banned in some states, like fireworks, but are allowed in others. This can be the case with these products. Like smoking, these products can be banned in certain areas, like restaurants.