Although the Milky Way Galaxy was relatively remote and barren, with no noteworthy civilizations nearby, the Nine Realms were still quite famous throughout the stars. To keep watch on Asgard's movements at all times, the Three Great Empires had established outposts along the edge of the Milky Way Galaxy. Whenever they wanted to send people there, they would teleport directly to those outposts.
But arriving in the Milky Way Galaxy did not mean they could enter the Nine Realms directly, because the dimension they could teleport into was a relatively desolate one, with practically nothing in it.
The Nine Realms had a rather unusual structure. Anyone using jump technology could only enter Asgard. In other words, those outside the Nine Realms had no way of teleporting directly to places such as Midgard or Vanaheim; they had to transfer through Asgard.
To teleport into Asgard, one had to obtain the current Asgardian God King's consent. This was not because they had placed some protective magic over Asgard, but because that was simply the nature of the World Tree. This protection came from the laws of the universe, and even the Three Great Empires could not avoid it.
And if they did not use jump technology and simply flew straight in, they would never be able to enter the true territory of the Nine Realms. They simply could not access the dimension where the World Tree was located and could only circle around within this barren dimension.
Any cosmic civilization that had received Loki's invitation had to reply in advance if it wished to attend, so it could obtain jump authorization. If a ship was not on the approved whitelist and still insisted on jumping in, it would bear all consequences itself.
Failing to jump in was one thing, but if interference