system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Trek] What inhabited planets exist in the various Neutral Zones? Since fleet ships can't enter the Zones typically, who do they trade with? Who defends them?
gpt
Warships cannot enter into neutral zones without violating treaty, but merchant ships can. These civilian trading vessels can go anywhere they please, albeit with some possible risk as civilian trading vessels are unarmed and thus helpless against a warship.

The civilian merchant freighter, Kobayashi Maru, is perhaps the most famous example of this. It can enter any neutral zone it likes without violating treaty because it is an unarmed civilian merchant freighter. The downside to this is that it relies entirely on the goodwill of warships to not fire upon it, and to protect it should it need assistance.

Any Starfleet vessel is still a warship. Yes, their primarily mission is not war, but they still carry massive amounts of armaments and shielding. Even a Starfleet science vessel is still extremely heavily armed. They are warships in all but name.

Colonies will typically build their own militia or planetary defense forces. The larger and most established the colony, the more elaborate their militia will be. A planetary militia commonly uses sub-light ships. This makes ships cheaper and easier to construct and because these ships do not need to travel to other planets, there is no need for FTL.

Bajor is an example of an independent planet with its own militia. A planetary militia is of course completely outmatched when it comes to that of any star system spanning empire, but such a planet isn't helpless. Not entirely, at least.