Steve-O is doubling down on his anti-SeaWorld campaign -- declaring the cops have no case against him because his freeway sign protest is a legal "gray area."
TMZ broke the story ... the CHP is recommending the San Diego D.A. prosecute Steve for vandalism and trespassing after he changed the exit sign last month ... from "Sea World Drive" to "Sea World Sucks."
Steve-O called in to TMZ Live Friday to say he believes there's no case against him ... because his crime was ultimately harmless. Best of all, he dared cops to arrest him when he returns to L.A. -- but you gotta see how he did it.
He better hope the police aren't watching.