User blog comment:Legionwrex/Usless Power./@comment-743796-20110521165915/@comment-3061137-20110524003342

I think the Lore behind the removal of the mods is that in the 2 year gap weapons have been "upgraded" with the heat sinks and probably some other changes making weapon moding more difficult and thus it requires training.

I think that some of the meapon mods will return for ME3