Is It Legal to Shoot a Looter?

Which is a good question. The answer appears to be, "No". If you shoot a looter who is not threatening you, i.e. if you take the law into your own hands and go defend the nearby Piggly Wiggly and manage to kill someone, you could be prosecuted if caught. The following citation is from Louisiana Law. Other states may have different rules, but in LA at least they have thought this through and made a decision against vigilantism.

Note, it is perfectly legal to defend yourself and your property, just not legal to deputize yourself and go on a hunting party.

Thanks to volokh.

Perhaps you'd care to provide a cite?

yes, perhaps I spoke to loosely, just citing the common law rule. Obviously, different states have different rules with different nuances about when deadly force is justifiable. Louisiana's law is La. Rev. Stat. 14:20.

A homicide is justifiable:
(1) When committed in self-defense by one who reasonably believes that he is in imminent danger of losing his life or receiving great bodily harm and that the killing is necessary to save himself from that danger.

(2) When committed for the purpose of preventing a violent or forcible felony involving danger to life or of great bodily harm by one who reasonably believes that such an offense is about to be committed and that such action is necessary for its prevention. The circumstances must be sufficient to excite the fear of a reasonable person that there would be serious danger to his own life or person if he attempted to prevent the felony without the killing.

(3) When committed against a person whom one reasonably believes to be likely to use any unlawful force against a person present in a dwelling or a place of business, or when committed against a person whom one reasonably believes is attempting to use any unlawful force against a person present in a motor vehicle as defined in R.S. 32:1(40), while committing or attempting to commit a burglary or robbery of such dwelling, business, or motor vehicle. The homicide shall be justifiable even though the person does not retreat from the encounter.

(4)(a) When committed by a person lawfully inside a dwelling, a place of business, or a motor vehicle as defined in R.S. 32:1(40), against a person who is attempting to make an unlawful entry into the dwelling, place of business, or motor vehicle, or who has made an unlawful entry into the dwelling, place of business, or motor vehicle, and the person committing the homicide reasonably believes that the use of deadly force is necessary to prevent the entry or to compel the intruder to leave the premises or motor vehicle. The homicide shall be justifiable even though the person committing the homicide does not retreat from the encounter.

my quick read of that suggest that defense of property, by itself, does not justify deadly force in Louisiana. A quick glance at the case annotations on Westlaw suggest that the touchstone is a "reasonable belief in danger."