He’s against it:
Samuel L. Jackson has just recorded a radio spot against Prop 8.
Unfortunately, it did not include the following:
“Everybody listen up! We have to put a barrier between us and the snakes! The path of the righteous man is beset on all sides by the inequities of the selfish and the tyrannies of evil men. They just trying to put a fright in your ass. RE-spect! Now, who’s the bad guys? And who’s the good guys? “