'You took an oath to uphold the law and defend the citizens without fear or favor,' said Vimes. 'And to protect the innocent. That's all they put in. Maybe they thought those were the important things. Nothing in there about orders, even from me. You're an officer of the law, not a soldier of the government.'Sam Vimes in Night Watch by Terry Pratchett
In the Annotated Pratchett, the entry for Night Watch outlines parallels with Les Miserables, and a point is brought up which states:
“Javert, the policeman in LM, is concerned only with justice, which he defines as the punishment of the guilty. Vimes, the policeman in NW, is equally obsessed by justice, but he defines it as the protection of the innocent.”, which I think is an interesting distinction and which seems to be relevant now.
He gave Vetinari a look that said: If you take this any further, I will have to lie.
Vetinari returned one that said: I know.