Piracy, raiding and the artful practice of taking something not yours.

  In Levis, part of trade, part of long distance moving and shipping is the expectation of the tithe. The tithe (known by a distinctive foliad name) is that part of the cargo expected to be lost to the 'illegal' act of taking what is not yours. Called piracy when on the open waters, and raiding when on land, Levis had a long history of such activities before the demons came - the demons just proved they were better at it.
 

Honesty is the best policy

The way things are done, is that resistance is always expected, though it is bad form to kill someone, both sides seeking the way of the animal kingdom - defenders going 'It is too much hassle to attack us' and aggressors going 'You'd best roll over before I get rough'. The cargo is transported openly, with only the things that cannot be lost hidden away.
  If a raiding party finds no cargo, it is only then that society deems it ok to dig and search further, for some things Need to get through, or the effort to acquire them too great to lose. In these cases it is advisable to travel with something you can offer up, should you get caught.
 

What is not yours

Theft within a domicile is frowned upon, and often dealt with by community service - most commonly to the person stolen from, with incentive that the thief not become a repeat offender. This does not mean it does not happen - often the purview of bards and their nighttime dealings.