There were actually a few races banned.
One of them was one of the races humans call "The Greys" who used to be creating hybrid people with the use of particular humans.
There were two races visiting Earth who humans called "The Greys" whose appearance was somewhat similar to one another, who were both creating their respective hybrid races with the use of particular humans.
Both of them were told by the organization of visiting races that they had to stop doing that.
One of them complied and the other did not.
The one who did not, was banished from visiting Earth.
The one who complied was happy to be able to get what they need in other, more advanced and appropriate ways from the organization of races, instead of using humans.
The rest of the races who were dismissed from visiting Earth just had no good reason for being here in the first place, and some of them were bothering humans.
Alien abduction was at one time rare.
Of the hundreds of alien races visiting Earth and working with humans, a few were doing things they should not do, and doing them in ways they should not do them.
There are no longer any more "abductions" going on of any humans by alien life.
But, still, in humans' minds, any alien contact may be synonymous with abduction.