not as easy as that. Clay is first 9 and helped started and expand the club. You just can't kill him without proof.
obviously if he takes it to the club he needs proof. my problem is jax is all over the place these days. its sloppy writing and it only serves the agenda of the plot. it seems like the only thing he's doing by the exact laws of the club is his handling of clay, everything else is all shady side agreements.
even if he has proof of what clay did, they're still going to have to do some cover up story if they kill clay. a first 9 killing two other first 9s would be a huge blow to the entire MC if the truth ever came out.
if jax is going to act out of character and irrationally because opie got merked then atleast make it consistent. one minute he wants to be cool and calculated the the next hes minute screaming and yelling like an emotional bytch and killing soldiers who were just following orders