Some reflections about the link between "armées de masse" and breaking of laws of war :

- the austrian landwher in 1809 did not lead to significant guerillas movements, but added number to the austrian line army. We can nearly say the same of Napoleon Garde Nationale in 1814 and of the prussian landwehr from 1813 on (with perhaps a worse record of pillaging in France 1814 and Belgium 1815).

- the french "levée en masse" was used to maintain the revolutionnary power against the coalised armies of Europe and the inner civil war in Vendée and Britanny. This was legitimate once you consider people like citizens, not just subjects. And it avoid to France a foreign invasion and the return of the unjust and baseless "divine right monarchy".

- any army, when badly fed, resorted to pillage. In this aspect I really don't believe that regular armies where less armfull to civilians than the conscription armies. XVIIIth "professional" soldiers were badly supplied and paid, with a recognized right of pillage in certain circumstances, and an high level of desertion.
About profanation of others' religion, rape, burning and pillages they did not wait anyone, to the point that after one year or two, armies had to move to comparatively spared territories to go on fighting. And the professional pillagers (housars, cossacks, uhlans, corps francs) were invented prior to the Revolutionary and Napoleonic Wars, to give some "little war" capacity to clumsy line troops.

- resistance to french invasion in Spain began prior to pillages and molestations :
. spaniards rised the Dos de Mayo because their independence was endangered, and their newly chosen king Ferdinand brutally deprived of power, when he represented the nation hope in a better government.
. even when the french army was torelably disciplined, like in Aragon under Suchet, guerilla went on fighting simply because the French were invaders.
Spanish national resistance deprived the french of local support and ressources, which started the cycle of guerillas/counter-guerillas war.
Collapse of logistic in Spain was a consequence of popular resistance, not a french system of war. Or why did not Northern Italy and west Germany, so many times the theater of war, turn into permanent insurgency ? (by the way, I think that the logistic of the french army, able to move faster than any other and to fight successfully hundreds of miles of its bases, with tons of bullets and powder carried by land, is grossly underestimated).

- laws of war were relatively recent in 1800 : nothing of that sort existed in 1618-1648, when 1/3rd of Germany was killed in war, or when Turenne destroyed the Palatinat as a dilatory action.
They could not apply correctly when popular resistance opposed foreign invasion : they stipulated that civilians who chose to fight without uniform were liable to death as rebels (hence the letter of french govenment to the Allied commanders in 1814, to avoid the shooting of Garde Nationale captured in peasant jackets - "blouse").
Thus anytime this kind of resistance arouse (in XVIIIth Cevennes, Scotland, Corsica, America, Poland; in 1793-1815 Vendee, Piemont, Ireland, Calabria, Portugal, Spain, Tyrol, Russia, east France on a lesser scale; in XIXth Italy, Poland, Hungary), the regular army had a legal baseground to resort to "examplary" retaliations : house burnings an summary executions, not only of fighters, but of "rebelious population" at large.
A morale case not even settled in contemporary time, when you consider Resistance in WWII and Algeria Indepenence War (to remain politically correct).

Hoping to contribute to the debate.

Kind regards,

Jean.