I am rereading Sargasso of Space by Lady Andre Norton for the first time in thirty years. I got it on iBooks and almost immediately regretted losing my copy so long ago. I forgot how well the author wrote. She had a simple and concise style that got the heck out of the way and let you enjoy the setting and the story. I was never one for stream of consciousness on every page or a dissertation on tech or sociology that the author was far more interested in than the reader (me).
I'm reading through the Solar Queen novels to mine them for a game setting, mostly system agnostic at this time.
So far it appears that Trade (not Merchants) is a very old and established service and similar to a Guild or Union. It provides training for new personnel (the Pool) and amenities like a restaurant in some ports. It also has a high degree of nepotism. Having family in the Service is almost a guarantee you will be accepted. The main character, an orphan, made it into the Pool and considered it a great achievement. It may be a matter paying for your education with some people qualifying for scholarships due to grades or charity.
The characters refer to their occupation as Trade or more commonly the Service. this is a little odd for merchants out to make a profit. I read a little further and the Trade personnel were all supposed to take X-Tee contact classes. The protagonist, Dane Thorson (yes he gets kidded about the name), is an apprentice cargo master. He has taken a number of psychology and economics courses along with a smattering of everything else. As a Free Trader his ship operates mainly on the Fringe and contacting new sentients, combat, disease and all your mundane dangers of space travel are a fact of life. The big companies stick mainly t the central regions and established trade routes with sure profits.
The Free Traders sound like an amalgam of Scouts and Merchants. It's not a matter of everyone doing what they want fueled by big business. The Service has trained the personnel to make contact with new societies in a friendly and responsible way. While people buy, beg and steal trade rights to new worlds they have training to deal with contact problems.
So far it seems the Federation the characters like in have three branches responsible for interstellar exploration and expansion. The Survey charts new worlds and performs a cursory inspection. While some worlds will be kept secret or declared off limits. After the worlds are charted and surveyed this information is made to Trade who then proceed to ... trade finding resources, contacting natives and setting up a merchant relationship. The Patrol is the big stick of the Federation enforcing a number of civil and criminal codes. Traders send Patrol HQ their passenger lists for one thing for the Patrol to perform background checks. Being Patrol Posted means you are in effect an outlaw and anyone can shoot you on sight with no legal repercussions. So much for due process on the frontier. The Patrol also has the unwanted duty of shoving plague ships into suns (a gas giant won't do.) The Patrol also attempts to keep war from breaking out between Federation members. At the time of the book Earth and Mars are still being watched carefully by the Patrol and Trade after concluding the 'Crater War' ten years previously. Trade was also helping to keep the peace so apparently trade is an adjunct to diplomacy. I doubt Trade makes demands of its megacorporations regularly but I'm sure they could get all the traders together to enforce an embargo on a world or exert other economic weapons to keep the peace.
I'm going to be working on applying these ideas to Traveller Merchants and Scouts next.