Castillo is a frequent critic of the council.
Councilwoman Claudia Alvarez said Castillo went beyond criticism and into personal attacks.
"I am not stopping you from freedom of speech," Alvarez said before the vote. "I'm stopping you from personal attacks."
The attorney general's office told The Orange County Register that it's investigating whether the incident violated open meeting laws.
Santa Ana's city code states that people can be kicked out of council meetings if they disrupt "order and decorum." Citizens who speak are warned they should address the council as a whole and not make "libelous or slanderous comments."
AP contributed to this report.