Does Mass Effect provide a lore reason why you can't use enemy weapons?

Question

Is there a reason given why you can't just take weapons from enemies that you've killed? For example, in the Metal Gear Solid series they (sometimes) state that enemy weapons are locked, through DNA or nanomachines or some such. Obviously, this is so the player can't just take an assault rifle from the first mook he sees and start blasting, but they've used the lore of the series to try and justify it. Is there a Codex entry that states something similar happens in the Mass Effect universe? I can't find anything on the Wiki that states why you'd have to wait until you find a weapon just laying around to be able to use it.

For instance, in ME2 you get the Vindicator from a couch in Archangel's base. At this point in the game you might have killed dozens of Blue Suns mercenaries who have been equipped with Vindicators. What's so special about the one on the couch?

Note that this may not be the case for the first game. It's been so long I can't remember if bodies were lootable or if it was just crates etc.

Answer 1

To the best of my knowledge, there is no definitive answer to this. In the absence of canon, I turn to speculation.

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For starters, Shepard did pick up every weapon they found in Mass Effect (the game, not the trilogy). This tended to rapidly fill the inventory with useless junk, but that's gameplay, and OP is asking about the story. In the other two games, weapons can only be picked up at specific points (far more often in the third game than in the second).

So what changed between the first game and the other two? Simple. Weapons were totally revamped between ME1 and ME2. The primary effect of this was to switch from a cooldown system to a clips-and-ammo system (for most weapons; some ME3 DLC contains weapons that cool down). This was justified by claiming the new system allowed guns to fire with more power, and that it was based on geth designs revealed during the events of ME1.

We may suppose that, as part of the changeover, weapons manufacturers pushed some new security features, such as the omni-tool lockout OP suggested in the question's comments. This sort of behavior is not unheard of in the real world. With the United States' imminent switch to chip-and-pin (and/or chip-and-signature), it is widely anticipated that NFC payments (tap-and-pay, Apple Pay, Google Wallet, etc.) will gain widespread support as well, purely as a side effect of vendors upgrading their POS terminals. It is plausible that weapons in the Mass Effect universe could benefit from a similar effect.

Answer 2

There isn't any mention in the games about any kind of lockout. The reason why it isn't in the games is primarily just for game play reasons, not lore.

Some of the games offered mid-mission weapon terminals that allowed you to switch guns you may have picked up from crates. So technically they could enable it; the game play designers probably didn't want to 'force' you to play on the higher difficulty levels so that more enemies would spawn so you would have a better chance of picking up the gun you wanted. Instead they chose to make that a non-issue by putting the weapons in static pickups instead.

However, back to the lore part of your question:

There are several instances in the Mass Effect books where the protagonist will pick up enemy weapons and use them. Though sometimes they don't. Usually it is based on what situation they are going into. If trying to stay stealthy, they'll keep their pistol. But if the protagonist has followed someone with only there pistols, but ends up in a situation when they're entering a warehouse full of Blue Suns and don't need to keep a low profile anymore, the protagonist will pick up the enemy assault rifle for himself or someone who is with him.

(This example is a half contrived, half plot example from the first book in the series, Revelation. I paraphrased instead of quoted so there wouldn't be any spoilers.)