Where can I read the rules on practising law for others in California?
Answered for: California
No person shall practice law in California unless the person is an active licensee of the State Bar.
This is California's rule on who may practise law. It is written about practising for other people; what it leaves unsaid, this entry does not fill in.
This answer is true in California and nowhere else on this site. Another jurisdiction is another answer, or an honest gap: see what has been read for California.