It is NOT foreign policy that they try to enforce against other warp-capable civilizations.

But this is not about foreign policy! This is about developing planets within Federation space. (Federation space is a specific region of the Alpha and Beta quadrants and may refer to both members and non-members!)

The only reason I ask is because the Fan page for the Federation says they enforce the prime directive on any invaders in fed space. I think False Profits is probably the only example that I can think of! Enterprise is pre-federation and pre-prime directive unfortunately.