I found this on the Happy Campers website:
Important Note for California RVers
While Happy Campers contains no formaldehyde, glutaraldehyde, bronopol, or other banned biocides, California’s SB-317 labeling rules restrict its sale there due to broad definitions of “non-biodegradable” chemicals. Always check local regulations to ensure your RV tank treatment complies with state requirements.
Next time you travel out of state, you could pick some up. I like Happy Campers, but there are others too. Unique is another popular option.