Traveller cannon does have several good publications about how Starports work, particularly John Ford's
GT Starports. However, I am more interested in what the actual crossing is going to be like, how to relate the Starport to the local society, and my views on rules and regulations that exist in Starports. From the various sector books, I see three major kinds of Starports. On major worlds where the Imperium is a considered a benevolent presence, you have what I call a 'Ramstein' type port, where the locals and the Imperium mostly in harmony. Where the Starport is seen as a 'necessary evil', the Starport resembles 'Cold War Hong Kong'. Also, small Starports may be established to set up a claim to a territory, not unlike colonial St. Augustine, FL.
What I'm calling a 'Ramstein' port is not unlike the US Ramstein Air Base in Rhineland-Palatinate, Germany. It is a locality under control of a separate sovereignty, but a close relationship between the two is maintained. Frictional issues between the two are routine, and rarely end up shutting down the port. This is a gross oversimplification, as there will be issues between authorities. Roads and construction standards in the port conform to those in the surrounding area, and local symbols are displayed alongside those of the Imperium. The largest difference would be a mandatory use of Anglic on all signage. Otherwise, with languages, the Starport will use Anglic, and there is a high possibility the locals will have some understanding of Anglic, if it isn't the primary language While checks do exist crossing the line, they are more around ensuring authorized personnel come in and out, customs regulations would be applied inside the starport's lines for the most part, rather than at the line. Concessions in the port will do most of their business in Imperial Credits, but the local currency maybe used by some, particularly 'temporary' concessionaires, like the burger truck that stops by the tramp pad. Local currency, if used, can be bought and sold at fairly reasonable rates. This is the ideal for many worlds.
A 'Cold War Hong Kong' port is one where the Imperium has an uneasy relationship with the world government for a multitude of reasons, such as local isolationism. One example is a large urban area is present inside the extraterritorial line, and the line is a heavy duty border. In some cases, the local authorities find the idea of a 'open commercial zone' useful in obtaining information and hard currency from off-world, and others, it is 'minimize cultural contamination" from offworld. Either result is similar, with a large scale startown, a hard line, and people wanting to cross it for a variety of reasons. Building and road standards maybe radically different, resulting in electrical goods from the Startown requiring extensive modifications to operate properly across the line. Linguistically, Anglic will be used for business and law in the enclave, but the local language may have be used as well, especially if there is a 'thaw' in relations. Currency will almost always be different across the line, and exchange rates will be rigged to reduce offworld purchasing power, unless you hit the black market...
A 'colonial St. Augustine' port is an outpost of the Imperium. Small, mostly a garrison, and the presence is there to claim a location. The locals and the port community rarely acknowledge each other, and there may be turf wars if a sophont is a 'local' or an 'Imperial'. Money may not be that common, and if it's there, the preferred tender would be Imperial Credits, or whatever the garrison is paid in. Also, anything for a trader would be very difficult to find, as distant outposts rarely have trade goods worthwhile. There maybe other settlements, many of them a long distance away, or others hidden on the world. Remember, a planet is a very large place, and it would be possible to hide a society for a long period of time.
In role-playing games, it seems players have an expectation of being able to take weapons wherever they please, and extraterritoriality often means Starports are assumed to have a low law-level. However, this wouldn't be much of the case. Generally, unless carried concealed, locked for transit, or authorized by the management, carrying of weapons is prohibited. This is mostly a safety measure, as a Starport with excessive violence is bad for business. An example of authorized carry would be a Mercenary officer assigned to work with the security force while his unit is on liberty. The mere act of transportation, such as a hunter on a safari expedition, is guaranteed through Imperial Commerce Regulations. Also, most Starports from Class C up do have at least one 'Outdoor Equipment' concession, that offers a wide variety of weapons, as well as more pedestrian survival equipment, that delivers inside the line, with containers sealed and ready for transport. The Starport Authority has an extensive corpus of laws and regulations built up over millennia, with commentaries available when needed. Generally, there is a procedure available for any situation, up to, and including doomsday incidents. As for goods import, ships and containers 'under seal' and transiting can carry almost anything. However, the Imperium does frown upon importing things that threaten life on world, generally, if it would cause death and destruction on world, the Starport may even ban a craft from landing. Remember the first rule: does it make sense at the gaming table?
These are just some connected ideas I have had on Starports. There are some that are part of but separate from the worlds they are on, some that are barely tolerated, and some that are staking a claim. I also gave a few thoughts on how I see Starports run, particularly with respect to weapons laws. These gateways to adventure are places to run adventures out of, as much as the class fantasy gaming tavern.
