[PeterisP]

The baseline for common rules is something that would be desirable by all major players.

Gas attacks and torturing POWs is something where the disadvantage of being on the receiving side is much greater than the practical advantage of being allowed to use such techniques, all major combatants would generally prefer to fight in a war without poison gas or tortured POWs, so they're prohibited.

For at least some "serious players", the practical advantage of being able to use or threaten cyberwarfare (or nuclear attacks) is greater than the disadvantage of potentially being on the receiving side, at least some major combatants would really prefer to fight a war where cyberattacks against civilian networks are used, so they can't and won't be prohibited or meaningfully restricted; the suggestions are simply futile unless they somehow manage to show that all the countries who currently seem to benefit from unrestricted cyberwarfare actually somehow suffer from the status quo.