In keeping with the case law mentioned by coureges and having in mind that police in our state still try to arrest for OC when it is not a crime here is a US Supreme Court decision concerning qualified immunity.
Harlow vs Fitzgerald,457 U.S. 800 (1982)
"If the law is clearly established at the time the action occurred, a police officer is not entitled to assert the defense of qualified immunity based on good faith since a reasonably competent public official should know the law governing his or her conduct". 8-1 decision!
Louisiana does not offer qualified immunity to it's police--only partial immunity.Most police are not aware of this or even know what qualified immunity is.Local courts will generally permit various amounts of foolisness/marginal actions.But when you haul one into Federal Court for civil rights violations the picture changes in your favor.The officers simply cannot justify their actions when case law is so well established to the contrary.