The reapers have returned from dark space. With Earth under attack and the mass relays in a state of chaos from refugees and the councils fleet engaging reaper forces the galaxy is a mess. The outcome is unknown, the warfare is devastating. The galaxy will never be the same.
Using a sophisticated IFF system, and the largest Systems Alliance Mass Effect Core. This little device creates a extremely large inverse Mass Effect field, rendering any unfortunate ship passing through it without the required IFF at a huge disadvantage. Without a working Mass Effect core, ships are not capable of FTL or active kinetic barrier systems.
Very clever.
You would be a good mech-e