 Why are the Soetti allowed to board the ship?
"It is rather unusual," Magnan said, "to assign an officer of your rank to courier duty, but this is an unusual mission." However, they lie deep in the sector into which the Soetti have been penetrating. "Now—" Magnan leaned forward and lowered his voice—"we have learned that the Soetti plan a bold step forward. Since they've met no opposition so far in their infiltration of Terrestrial space, they intend to seize Jorgensen's Worlds by force." Magnan leaned back, waiting for Retief's reaction. Their industry is limited to a minor role in their economy—enough to support the merchant fleet, no more. "The Soetti War Plan—in detail. Overall policy calls for a defense of these backwater worlds. Otherwise the Corps would allow history to follow its natural course, as always." Retief opened the envelope Magnan handed him and looked at the tickets inside. The Soetti are patrolling the trade lanes into Jorgensen's Worlds; don't get yourself interned." "You'll be traveling with Class X credentials," Magnan snapped. VIP's required accommodation," he said. You'll have to try to get space on the Four-Planet Line ship next—" "Which gate?" "But—" Retief picked up his suitcase and walked away toward the glare sign reading To Gates 16-30 . Retief followed the signs, threaded his way through crowds, found a covered ramp with the number 228 posted over it.
 The captain and Mr. Tony are in business with them.
 They need transport to Jorgenson’s Worlds as well.  They need to check the papers of each passenger, so the caption allows them to do so.  The Soetti aren’t - the captain fears them and they are illegally boarding.  The captain and Mr. Tony are in business with them.