Ideally, one should be prepared with stocks of food and other supplies so as to avoid any temptation to steal.
Apart from any legal consequences when order is restored, remember that looters may be shot ! either by the owners of the property or by TPTB.

There are of course circumstances when breaking the law might be acceptable, but IMHO these apply more to the breaking of minor regulations, rather than to looting or other theft.

Connecting up a standby generator without permit or inspection (provided that you know what you are doing) is against the law in many places, but in an emergency is a lot more acceptable than looting.

Theft or other crime MIGHT be acceptable in dire emergency if the alternative is death, the example given of breaking into a vacation home is a good one.

Likewise, if hungry, the shooting of an animal to eat it is probably acceptable even outside the hunting season.

Morally it is a bit more acceptable to steal things that would otherwise go to waste, for example crops that are clearly not going to be harvested and will otherwise rot.
If you neighbour dies suddenly, to steal the contents of their home is wrong, the goods belong to their family. But harvesting their garden crops might be acceptable, especialy if they would go to waste before the property is sold.