Forum:If Shepard did not do Arrival on ME 2 then what's the justification for keeping him/her on Earth on ME3?

In the beginning of ME3, Shepard is on Earth to answer for the destruction of the Bahak system on ME2:Arrival.

If you didn't do Arrival on your ME2 import then apparently Hackett sent a bunch of marines to retrieve Dr. Kenson but they all died anyway.

Hence, the title question. Anybody want to fill me in on the details? I don't think this topic has been discussed yet given the ending sh*tstorms and all. :/