In Animal Farm, who breaks the commandments, 'Whatever goes upon two legs is an enemy,' and 'whatever goes upon four legs or has wings is a friend', and how? What justification is given for breaking these rules?
It is the pigs, the rulers of Animal Farm, who break both these rules and indeed every other rule originally enshrined as the guiding principles of the animals' revolution. These two rules in particular are designed to unite the animals against their common oppressors, the humans; they are condensed into the slogan ‘Four legs good, two legs bad’. However, the pigs, in their abuse of power end up playing entirely false to this principle.
It can be seen how the rule about ‘whoever goes on four legs or has wings is a friend', is broken almost from the beginning by Napoleon and his supporters, during his great rivalry with another pig, Snowball. Napoleon and his second-in-command Squealer end up painting Snowball as being an even greater enemy of Animal Farm than the humans, whereas he was really one of its greatest champions.
Then the way in which Napoleon and the other pigs turn against other animals is seen in the shocking series of purges when various animals who had previously dared to question Napoleon's ideas are slaughtered. This is most certainly not a case of viewing all other animals and birds as friends, but the pigs justify their repressive actions by pretending that anyone who dares challenge them are deadly enemies of the Farm and therefore must be eliminated. This kind of propaganda helps to keep the other animals quiet.
Finally, the pigs sell out altogether when they take up trading with humans again, while keeping most of the other animals well under. In fact, they actually start to physically walk on two legs themselves, like the humans whom they now openly mingle with. When the other animals first see them walking upright, they watch in stunned silence.
Then there came a moment when the first shock had worn off and when, in spite of everything–in spite of their terror of the dogs, and of the habit, developed through long years, of never complaining, never criticising, no matter what happened–they might have uttered some word of protest. But just at that moment, as though at a signal, all the sheep burst out into a tremendous bleating of–
"Four legs good, two legs better! Four legs good, two legs better! Four legs good, two legs better!" (chapter 10)
As is clear from this quote, the animals are so shocked at this utterly blatant betrayal of the original principles of the revolution that, almost for the first time, they are moved to object to what the pigs are doing. However the sheep, who always mindlessly repeat the pigs’ propaganda, once again prevent any opposition. Their bleating simply drowns out everything else. And by this stage the pigs are so powerful they don’t even need to make a show of justifying their betrayal of the original principles of the revolution. They simply change the rules whenever they feel like it and the other animals can’t do anything about it.