My question involves name change laws in the State of: California

My husband is getting plagued by emails from his ex girlfriend. Long story short, they split up for 3 years, she came to him 2 months pregnant, he wanted to make things work, she's a lying, cheating (insert word here), and after the baby came, DNA proved him not the father, which they all knew, and he signed the birth certificate. A few months later, she split. Now, she's married, and her husband wants to adopted the baby. How can we get my husband of the birth certificate? She said she was sending him papers, and it never happend.

How do we go about getting his name off the document and finally getting rid of the (insert word here)?