Not to overlook the little irony of the new liberty enjoyed by the French soldier rather complicating the matter of protecting the foreign peasant.
Wellington was well aware of the absolute need, if his strategy was to succeed, of not upsetting the locals (hearts and minds) and he had the lash and the noose to enforce his policy. It is noticeable that was not over anxious to use these after a succesfull seige, however.
The French, on the other hand, had a number of years 'enlightenment' behind them which may have introduced the guillotine, but removed the lash.