During the hundred years war, particularly the period after Jean II was captured at Poitiers, there was a fairly severe breakdown of order in France.I think this period would be interesting for you to look at.

The ongoing conflict was not only between the French and English Kings but involved proxy wars involving French and English aligned factions in Brittany, involvement by both sides in the Castilian Civil war, and French dukes

Following Poitiers there was ostensibly a truce, but routier (mercenary) companies, particularly those who had been English aligned continued to rampage through the French countryside, at a time when French royal finances and authority had largely collapsed.

Many of the routiers were prominent knights or captains whose companies had campaigned as part of the royal host, but would at other times capture towns or castles and extort ransoms or collect protection fees from the local area.

Medieval warfare, even for the most "chivalric" knights, was also a commercial enterprise, in which a man could get rich from capturing enemy knights/nobles and ransoming them. Routier bands might have campaigned with the Black Prince one year, then struck out on their own the next season, and then perhaps campaigned as part of the royal host the next season. So many of these groups moved around freely on a spectrum between the most official forms of medieval military service and outright banditry.

But behavior which looks like "banditry" to modern eyes in some cases had legal protection. There is an anecdote in Froissart's Chronicle where routiers capture a town and make them sign a contract to pay a ransom. The peasants flee into the woods to avoid paying, and the local lord has to roust them (with fire and sword) out of the caves where they are hiding because the agreement is legally binding.

The routier issue also highlights the English tactical brilliance but lack of Strategy during this period. Routier bands were a cheap and effective way to fight and weaken the French Crown, but post-Poitiers these mercenaries were one of the factors which undermined the extremely advantageous treaty and ransom the English secured from Jean II.

You can also compare the routiers with the Jacquerie, which took place around the same time, and was a peasant revolt which butchered local nobles, in part for their failure to protect the realm from routier groups and live up to their feudal obligations.