 Why did the Viceroy blockade the Earth if he wanted an Earthling to come and meet with him?
The sight of an Earthman on Vega III, where it was impossible for an outlander to be, brought angry crowds to surround John Crownwall as he strode toward the palace of Viceroy Tronn Ffallk, ruler of Sector XII of the Universal Holy Empire of Sunda. A pair of guards, their purple hides smoothly polished and gleaming with oil, crossed their ceremonial pikes in front of him as he approached the entrance. "Just tell him that a man has arrived from Earth to talk to him. "It's customary to genuflect when you enter the Viceroy's presence," said the standing one at last. What I meant was that I expected someone from Earth to break through our blockade and come here. "If you wanted someone from Earth to come here to see you, why did you put the cordon around Earth? There was even serious discussion of destroying Earth out of hand, while it is still possible. While these creatures could by no means be classed among the intelligent races, there was a general expectation, which we reported to the Sunda, that they would some day come to be numbered among the Servants of the Emperor. The men of Earth had decided that it should work in theory. They had headed for that planet confidently and unsuspectingly, using the ion drive. Two weeks later, while they were still several planetary diameters from their destination, they had been shocked to find more than two score alien ships of space closing in on them—ships that were swifter and more maneuverable than their own.
 The blockade was a test to see if Earthlings were smart enough to help the Vegans defeat the Sundans.
 The blockade was a test to see if Earthlings were smart enough to help the Vegans defeat the Sundans.  The blockade is there to protect Earth from the Sundans.  The blockade is there to quarantine the Earth. Earthlings may have diseases that could infect the other races.  The blockade is there to keep people from leaving the Earth.