Enforcing Loyalty has a potentially potent effect. It can trash any out of faction card in the runner's rig, Anything! But is it a good card? There are several points against it:
-Because of it's play cost, it is basically a trace 1 card. That is horrendously bad! You can bump it up by 2 for free in NBN: Making News which is a little more doable. Primary Transmission Dish could help too, but you'll need to protect it. You have to consider too, that more and more runners are wisely running with link. That makes it even harder to land this card. So to use this, you'll either have to catch the runner when they are broke or spend a good amount of credits.
-It's a double which just makes it more of an investment to use.
-It has a trash cost! And an extremely low one. That's right, this is one of the new breed of operations that can be trashed when accessed. This makes it vulnerable to being sniped out of your hand or R&D before you are ready to use it.
-It only targets out of faction cards. This would include neutral cards and so each deck does have a decent number of targets, but still far less than half of their cards will be target-able. And you won't know until you sit down and start playing which ones.
Now if you do catch the runner with no credits, you may be able to take out a vital, perhaps non-replaceable, part of their rig. You might target:
-A loaded Kati Jones.
-The console or other memory cards. This could be huge if they have a full rig, forcing them to immediately trash some programs. A Scheherazade or Leprechaun could have the same effect. Remember that any of these cards have to be out of faction though.
-Take out their Plascrete Carapace and then go for the kill.
-High cost cards like Femme Fatale.
As you can see, if you manage to pull it off, the effect can be devastating. Hence the many downsides to the card. It does only cost one influence so you can include all three of them in a deck easily enough. I think you could run a Midseason Replacements deck with Closed Accounts and a couple of these. Give em a bunch of tags, take all their money, then in the next couple turns take out parts of their rig. Of course if you pulled this off then you could probably just of Scorched Earth them.