See the article here:
Malibu Rodenticide Ban Enacted
And for more details on the efforts and reasons behind the ban:
Malibu Group Works to Break Rodenticide ‘Chain of Death’
National Park Service (NPS) studies have shown that rats who ingest the harmful chemicals can take several days to succumb to the poison, and often in the interim larger birds and mammals hunt and eat them.
“They’re wandering around with poison in [their] system, which can make them more of a target for prey animals,” NPS spokesperson Kate Kuykendall said, “so the prey animals could be more likely to eat them and then get the poison in their system.
“It’s a horrific death and no animal should have to go through that,” added Fuchser, who said that his own dog was a victim of rodenticides and died after eating a poisoned rodent. “I know pests are pests, but I think there are other ways of dealing with them and poison is just a lazy way out.”
The use of poison bait is a crude and ineffective way to deal with rats. Poison only deals with the symptoms of a rat problem - rats and not the cause - a situation that attracts and promotes rats.