Please observe the instructions in this post when visiting your local spaceport for your comfort and safety.
When you turn up for an interstellar flight you’ll notice the two lines painted on the floor at the checkin desk. The orange line is on the outside, and up to this line the law of your home planet applies. This is called P-side, P stands for Planet. Once you check in and step over the black line, which is on the inside, towards the apron where the space liners are, you are diplomatically in interstellar space, and everything is governed by the protocol of interstellar law. This side of the line is the V-side or vacuum side.
The lines make a complete loop around the sensitive parts of the spaceport, so you will see them again as you leave baggage reclaim at your destination planet. Customs are operated by the local planetary government and are entirely P-side.
Please don’t treat this as a free way of avoiding the consequences of a crime. If you’ve stolen something and dive over the line, the station manager will heave you back into the arms of the waiting cops. Contrary to popular rumour the Arcturian station managers don’t carry guns, at least not all of the time, but they do have the assistance of some very fit baggage handlers.
Political asylum is another matter entirely. The protocol explicitly forbids planetary governments from operating a secret police, so if your home planet has one you can legitimately escape by crossing the line. Once there you as as much protected as you would be in an embassy.
On behalf of Arcturian Interstellar Space Lines may I wish you a pleasant flight.