• brp scripts don't see the provides yet
• gating could be used, but many other things are forbidden and we don't gate on them :/

We would probably want to enable the RPM feature to run package checks post-build to trigger build failures for things that are absolutely out of policy. This is something that the Mandriva family has done for a long time with rpmlint, and we could do the same for a variety of things.

Sure, I guess implementation is of secondary concern here, and I probably should not have brought it up yet, because this is not explicitly forbidden, and the question is whether it should be?

It should be forbidden, yes. +1

This is already forbidden by policy, we just don't have a way to enforce it yet.

If rpm doesn't give is a way to hard-enforce this then I don't see why we wouldn't at least try to get a a gating test implemented. Of course, I have no idea at all how to actually do that.

It would also seem smart to have a rpmlint check implemented as well. That may well be easier, though I also don't know much about rpmlint development these days and whether this would be something added in the Fedora package or something sent upstream.