I always assume Imperial Government issuing all licenses in Imperial territory...through the appropriate military/civilian offices. Imperial license would override any local law enforcement.
Actually I have to say the Imperium usually only issues licenses for those things that occur within their domain...the space between...and leave ALL local regulations to the planets themselves. If players break the law on one planet, even if what they did was totally legal on the last planet they were on, then they are on their own look out.
This is one of the reasons startowns exist, to provide a buffer zone where ships crews can walk about without needing to go through all the rigmarole the locals have to go through.
One factor of law level that is not played up enough is the amount of bureaucracy a higher level often entails. A RL example is that while it is difficult to get a concealed pistol permit in New York City, it is possible. There are lawyers who for a few thousand dollars will help you through all the paperwork and court appearances needed. That is at least law level 9 in my book.
In some states the ability to drive as demonstrated by a written test and in car test is enough. In others you must also show proof of training and recent recertification on occasion. In yet others, and because of the 10th amendment, if your current one is valid, then you are good to go.
IMTU worlds on Mains will often have a degree of cross acceptance of each-others paperwork in most cases. The main difference will be in cultural, religious, political and other ‘traditional’ laws. Most “interstellar business law,” which would include many operator certificates for starships and some small craft, like the Air/Raft, will likely be accepted near the XT line. As you get farther away from the XT line, in both distance and time, the more the locals will want you to pay their license fees and re-cert with them.
Now if a PC is also a noble, there has always been the option of appealing to your next higher authority. But it is not always a get out of Jail free card. If you are new in the area, the local nobility may want to make an example of you and show the commoners that even the nobility is not above justice. If you know the local noble and have good relations with her, then perhaps you will get off with a warning or reprimand.
Keep trying to break the law and running to the Marquis and you will soon find that even that Knighthood won’t keep you out of jail.