I've know about that bug forever now, at least since 1.21 came out, and I STILL don't build the walls. Smart, huh? 

These very same civs are pathetically behind in the tech race and are just begging for me to nab their victory locations.
Fixed v1.21f:
...
* Fixed building prerequisites to allow buildings to require buildings that are bestowed by other buildings but only if 1 is required. If more than 1 or required, they must actually be built.
You're right, it most likely won't be changed. We've had similar problems with other buildings, and the approach has so far been, that we add in a second type of the building (let's call it Local Courts) and then let the wonder grant that, while retaining the Courthouse requirement for the District Courthouse. We may do something similar for the Courthouse, if we can be sure that the effects of the Local Courts and Courthouses would be cumulative.Originally posted by pdescobar
EDIT: Did some checking, this is a known issue and my guess is that it won't be changed. Quoting the vanilla readme:
Since the DC requires 3 courthouses rather than simply one in the city, it falls under the second clause.
Assuming that "Resistant to Corruption" was a typo for "Reduces Corruption" in the email zulu9812 posted @ CDG, the effect is cumulative.Originally posted by Isak
You're right, it most likely won't be changed. We've had similar problems with other buildings, and the approach has so far been, that we add in a second type of the building (let's call it Local Courts) and then let the wonder grant that, while retaining the Courthouse requirement for the District Courthouse. We may do something similar for the Courthouse, if we can be sure that the effects of the Local Courts and Courthouses would be cumulative.