In theory, the Inquisition is kinda supposed to be the oversight on most all of these (including, to some degree, itself).Q99 wrote: ↑2017-11-27 04:19am On your planet, merchants may have their own private military forces. Nobles often do. The planetary governor does, and separate from that, there's the Arbites (which are Imperial and do not hold direct loyalty to planetary authorities). The Church 'doesn't,' but can call up other stuff so it may as well. And by 'other stuff,' it can be asking for forces for others, but it can also be, and often is, angry mobs.
Pretty much any of 'em could murder a random civilian and have little consequences.
In practice? Manpower, corruption and bureaucratic inertia are always problems. One work-around to this is that individual Inquisitors have an incredible degree of freedom to do as they think best for the Imperium. Inquisitor Joe finds out that a high cleric is siphoning tithes for his personal army, there's not much stopping him from walking into the guy's office and blamming him. Unless it actively hurts the Imperium in some fashion (say taking a vital military commander off the front lines without a reasonable replacement), the Inquisition isn't likely to punish Joe for taking unilateral action like this, unless he can't come up with decent proof that the guy was up to no good. And there's probably an Inquisitor somewhere keeping an eye on Joe, and an Inquisitor somewhere else keeping an eye on both of them... but their authority isn't unlimited, and they do have to be able to prove their accusations and give evidence that their sentence was merited. These are the hard part and why Inquisitors will enlist people capable of penetrating all the strata of society to ferret out facts.