Torture has been banned by every reasonable warp-capable race. Even when earth was in the last fits of imperialism there was a general prohibition on torture that supposedly applied to everyone on the planet.1 The prohibition on torture arose to the level of jus cogens.2 This means that it was a peremptory norm that applied to all and there was no excuse for violating it. One would be hard-pressed to argue that insterstellar law has regressed to a point that torture is acceptable.
Fortunately, Captain Lorca escaped from the Klingons, but not before he was tortured by them. Past governments have tried to claim that using bright lights and other supposedly harmless techniques were merely "enhanced interrogation" and not torture. However, given that the Klingons knew of Captain Lorca's sensitivity to light, the other beatings, as well as forcing the prisoners to choose among themselves which one would get beat by the guards, they are certainly violating interstellar norms that prohibit torture.
The crew of the Discovery is a razor's edge away from similar crimes as well. Ripper -they even gave it a name- is most likely sentient, yet they continued to use it for the spore drive. Saru ordered the drive to be used even after Burnham, Stamet, and Culbert brought it to his attention that it would severely harm the Tardigrade. Saru even ordered that the Tardigrade be force-hydrated in order to get it well enough to navigate the spore drive again. Forced feeding, while not torture, can be pretty monstrous. Fortunately, it did not come to that.
Even if Saru shouldered the blame, like he said he would, those of us in a position to stop it would not have been spared punishment. There is a long history of holding individuals accountable for the war crimes they could have prevented. Many Japanese and German military leaders were responsible for the horrendous acts they could have prevented, or that they allowed to happen. But for Stamet's ballsy move to step into the device himself, and for Saru's decision to finally let the Tardigrade be healed, we'd all be on the hook. Might still be...
Side note: If Mudd ever gets away from the Klingons, he could probably bring a claim of false imprisonment against Captain Lorca. Unjust imprisonment is when someone's movement is restricted without justification or consent. When Lorca was escaping, he could have helped Mudd or even just left the cell door open, but he locked Mudd back up. Shoot, he could sue Lorca personally, or sue the Federation because Lorca was acting as a Starfleet Captain.
1 See Prosecutor v. Furundzija, Interstellar Criminal Tribunal for the Former Yugoslavia, 2002, 121 Interstellar Law Reports 213 (2202).↩
2 See Frowein, Jochen A, "Ius cogens," In Max Planck Encyclopedia of Public Interstellar Law. 2213)↩