Aaahhhh, the friend of a friend legal advise. That's almost as good as the some guy on a gun forum on the internet legal advise.
My thought is, La doesn't have a law against carrying rifles or other long arms. Why would they have a law against carrying a pistol in a "rifle caliber", whatever that is? Is a 9mm a "rifle caliber"? Because I know people with 9mm pistols and 9mm rifles. I know people who own .357/38 Special rifles and revolvers. I know some who have .22 caliber rifles and .22 cal pistols.
My policy is, if anyone is going to tell me that there is a law against me doing something that person is obligated to cite that law to back up his claim.