I've just found some material with a bearing on the issues, though not the particular incident. In context, it should be remembered that Catalonia had suffered heavily under the French (see Duhesme) and that Macdonald had been making efforts to conciliate the inhabitants up to this point.

Catalonia 1810 a town named Belpuig , in September 12 soldiers were murdered. Marshal Macdonald's proclamation of 22 Sept stated
" The priest of this town, the alcade, the regidor and sous-regidor , of whom the ministry of one and that the functions of the others should have led them to oppose these horrible attacks when they were known, applauded them and allowed the assassins to walk openly around Belpuig, covered in the spoils of their victims and receiving the honours of their crimes.'

The alcade was shot, the regidor and sous-regidor were hanged, 15 inhabitants were taken hostages, to be shot if the assassins were not handed over and a contribution of 10k piastres and 2k quintaux of grain was imposed on the commune.

Macdonald imposed a further order on the whole region:
" The inhabitants of the communes are collectively responsible for the crimes of assassination committed on their territory and on the persons of the French and their allies. When it is proved that a Frenchman or ally has been assassinated on the territory of a commune and that the assassins have not been seized and handed over to the army, ten of the inhabitants, the first found in the commune will be taken and will be hanged without any other form of trial in reparation for the crime; their goods confiscated and their houses pillaged and demolished; if there is resistance from the inhabitants they will be subdued by force and their commune pillaged and burned.'

Given the sexism of the period it can probably be assumed that 'inhabitants' meant adult males.
Since Macdonald was keen on the principles of the laws of war it may be taken that this level of reprisal was regarded as within the rules. He had made similar proclamations in Rome 1798 and Naples 1799 in very similar circumstances.

My source does not include any corresponding orders to the troops on discipline.

regards,

Susan