These are not immigrants, green card holders have always been eligible to enlist.
Illegal aliens have always been barred from enlisting, until the illegal Kenyanesian Usurper illegally allowed some to illegally enlist.
The Trump administration is trying to restore the rule of law.
This has had to be going on for a long time.
In the mid 50s when I was in the Army 3 German soldiers who fought against us in WWII were going this route.
Iwas close to one of them, and he hated the other 2 Germans, he would refer to them as "farmers" because when the Germans started to lose the war they took in civilians not normally suited for military service.
Even the pronunciation of the German word for "I" which is ich was an issue. -Tom