What's the security reason they need this? How many times has a security camera failed to do its job because it didn't have audio? What crimes do they thing they are going to solve? Are people breaking into the courthouse wearing masks but screaming their own names?
I think one problem is, almost all security cameras are sold with audio these days. If the cameras have a mic, telling people "Oh, we turned the mic off in each camera" or "We don't record the audio" isn't very helpful.
There’s another problem with this because a camera with a mic cable cut would look from the outside exactly like a camera with mic cable intact, and maintenance is a thing, so eventually it’s bound to be replaced by a camera with a working mic either by mistake or “by mistake” on purpose. There’s a trust issue here since people who would be affected by the presence of a mic won’t be able to easily visually verify that it’s disabled.