[0rph3u5]

How will the company or merc operate when their homes, logistic, families are all living under the GTVA?

1. The GTVA is a political entity founded to uphold a political treaty, the BETAC. As the entity assigned to the protection of the sets of laws that exist under this social contract, it is not allowed to violate them. Simply put, those how have to enforce the law, have to obey the law. The existence of law breakers does not suspend the rule of law.

2. The doctrine of the prohibition of collective punishment applies under BETAC. Long fancy words, made short: Under BETAC you cannot punish a person for the actions of another. Especially you cannot punish someone solely based on association, including family connection, legitimate business ties, and similar.

3. Internal enemies of the GTVA might shelter their logistics into "uncooperative populations", i.e. they might seek specifically to build their logistics base on planets which already have a strained relation with the GTVA. As a result any military or law enforcement action may be delayed by having to navigate the relationship between GTVA authorities and the locals.

4. Internal enemies of the GTVA might exploit the provisions set up for the oversight of civic institutions, e.g. the GTVA version of a "Freedom of Information Act", to gather intelligence and identify and exploit blind spots of the GTVA.

1, 2 and 3 are reasons that in the real world help organized crime to be successful against prosecution.

[TrashMan]

You are talking about organized crime that isn't staging open armed conflict/rebellion... or crime syndicates/organizations that are situated outside of the nation (and hence limit response options).
But since the GTVA is the sole government and there is no other nation to speak off, there would be little to stop the GTVA.

And even if once can obufuscate, ultimatively is the GTVA that has a strong hand in any discourse with locals. What local politican would risk pissing of the entire GTVA for some local pirate group? They could stall a bit, but let's not assume the GTVA would be above playing dirty itself. Accidents happen. 

[0rph3u5]

The methods are transferable. I was just being deliberately abstract because the go-to real world example I had in mind is ...very current (Hamas in Gaza).

That the GTVA is the only government doesn't make the population inside the GTVA homogeneous. Actually, it is more likely (and canonical due the fracture of the GTA) that the scattered populations of Terrans and Vasudans are very heterogeneous - not every frontier settlement is a model colony that strictly obeys the metropolis.

And the problem might not be the population directly affected. If the GTVA military were to conduct, e.g. a search and seize in a pacifist community, that community itself may not have direct means of resistance, but than on the other side of the GTVA territory just the rumor of that happening might ferment resistance where there previously was none, simply because smell of government overreach. 

As for the playing dirty part, that might work in the short term but it might deal long term damage to the authority of the GTVA that is entirely avoidable.

[Shivan Hunter]

FS's minimalist worldbuilding doesn't give much info about the structure of government within GTVA territory - we can easily conceive of multiple civilian governments of various colonies, each with different internal structures and cultures and attitudes, each a signatory to the GTVA. FS certainly doesn't preclude things like civilian police forces (a la Destiny of Peace's first mission), militarized fascist police forces, private security/mercenary corps, even potentially local militaries or militias that answer directly to a colony's civilian government rather than the GTVA itself. (Some of these are likely a point of tension between various colonies and GTVA leadership.)

Based on the very short FS timeline, colonization happened extremely quickly both before and after FS1, so there are reasons for all the colonies to consider themselves part of a single collective in some sense (including a common enemy: first the Terrans/Vasudans, then the Shivans). The GTVA's single-military-government structure seems like a relic of this time. Post-FS2, the culture is probably trending away from the desire for a single government, as various colonies start to establish their own cultural identities and want to manage their own defense forces. The GTVA could end up transitioning to a more NATO-style alliance of militaries rather than a single military entity unto itself, or its leadership might resist this change.

Keep in mind that there really is no "Russia" to the GTVA's "NATO". There are only two major political factions in known space and they are both part of the GTVA, so other than quelling the occasional violent rebellion, the GTVA's singular purpose as an organization is "Prepare for future Shivan invasion". Given how shortsighted people can be, I could easily see various colony governments questioning the amount of resources allocated by the GTVA for R&D and military construction that could be diverted towards welfare/civilian development.

[0rph3u5]

There is also another point I keep taking for granted in my line of thinking - basically, that I keep thinking about the GTVA less like a modern state with a fixed territory but more like a medieval kingdom, where the state authority only exist where the monarch physically is and the authority is greatly delegated (e.g. how, during the rule of the House of Staufen - 1130 - 1220 CE, the modern northern Germany was a playing field for ambitions princes, prosperous city states, and foreign monarchs because the court of the Emperor tended to remain south in Empire to project force beyond the Alps).

If you treat the GTVA in a way that is less centralized and with broad restrictions on centralized institutions, especially the military, it creates a long of places where the central authority doesn't reach and which local authorities can act with far more impunity, same for localized non-state actors.

[Goober5000]

That's a really interesting way of thinking about the GTVA, and it can certainly create some intriguing possibilities.  A lot of campaign writers take it for granted that the GTVA has a fairly strong, centralized, authoritative, and robust government; but framing it as a medieval kingdom is a fresh perspective to me.  A lot of things would be different - society, commerce, settlement, travel, exploration - and even things like the NTF Rebellion can be thrown into quite a new light.