Festrian Imperial Starport Authority

Starports in the Imperium are paid for, run and maintained by their host worlds, but they are overseen by the Imperial Starport Authority. All full member worlds of the Imperium have either A or B class starports, and all such will have regular offices of the ISA; this is also the case with Protectorate worlds with A or B class ports. Worlds with only C or D ports generally do not; E or X class worlds never do. The ISA insures that the starport is in compliance with Imperial law regarding extraterritoriality, safety and so forth, and also have an eye on cargo coming through the port. They are not responsible for customs duties - that is handled on the host world's side of the extrality line - but cargo is monitored to ensure that no Imperial law is broken.

One of the ISA's most important jobs is monitoring shipyards and ships under construction, to enforce Imperial controls on naval construction. The Imperium will not generally allow its citizens, however wealthy, to acquire warships. Certainly,  designs involving bay weapons, spinal mounts, heavy armor, unusually powerful drives or computers are unlikely to be approved. Naval architects won't accept such contracts; financing will be unavailable - but even getting over those hurdles, the an ISA officer has to sign off before the ship gets laid down. A civilian attempting to build a meson destroyer can expect a number of long interviews with both the ISA and Navy intelligence.

Full member worlds are expected, if able, to build ships for the Imperial Navy: naval shipyards maintain their own security to insure that military grade armaments are not diverted, or military secrets divulged.

The ISA office of a protectorate world's starport must monitor not only civilian, but the world government's military shipbuilding closely to make certain that they don't start building ships of the line for themselves or anyone else. The Imperium will allow a defense fleet for protectorate worlds in good standing, but generally this means no jump ships and no spinal mounts: nothing that can be used aggressively, and nothing that can stand up to an Imperial warfleet.

A world with the technology and resources to build a starship can do so without a commercial shipyard. Worlds within the Imperium may not. The presence or absence of a class A or B starport is an expression of a world's willingness and ability to participate in the interstellar community, but it is also a symbol of the Imperium's acceptance of the world into that community. So, within the bounds of the Festrian empire, a TL 12 industrial world with a C starport is quite capable of building jump capable starships, but it will be doing so in secret, and at considerable risk.

(Worlds outside of the Imperium are a different matter altogether: starport classifications there are equivalents only: there is no extraterritoriality, and the ports are governed by planetary law (or by their own interstellar governments'.) Shipbuilding on such worlds is governed entirely by technological and industrial ability, and the presence or absence of commercial shipyards is no indication of those worlds' capabilities. Since the sector I'm building is all Imperial space, that's a non-issue.)