My guess would be, the treaty you have with Tanganyika is causing this. I seem to have a vague memory of this happening before..
EDIT: I found a post by tkobo from 2010. He confirms SDI will take out ANY missiles flying over a region that has the Missile Defense, or treaty.
I and others have seen it work,so unless something has gone wrong recently.....One thing to keep in mind, this is SDI,not Iron Dome.
Last id looked,it would even shoot down your own missiles IF they traveled thru a region that you had the treaty with, and had the satellites.IE your satellites would shoot down your missiles because they in were the airspace of an ally with whom you had the treaty .....
As for why you can get the treaty even though you dont have the satellites ?Well, the party you want the treaty with could have them.And yes, it can appear quirky when neither has them.
Reference thread; viewtopic.php?f=43&t=16799&hilit=SDI