Well you'd have to ask the person who was using it (the "against ME" part would refer to them). I've never used the phrase, so I don't really have a meaning for it.
As far as the verse from Isaiah, the first thing I do with any verse is put it into its context.
If anyone attacks you,
it is not from Me;
whoever assails you
will fall before you.
Behold, I have created the craftsman
who fans the coals into flame
and forges a weapon
fit for its task;
and I have created the destroyer
to wreak havoc.
No weapon formed against you shall prosper,
and you will refute every tongue that accuses you.
This is the heritage of the LORD’s servants,
and their vindication is from Me,”
declares the LORD.
Then I like to look up a bunch of commentaries
and see what folks who have more education on the subject than I do have to say. (This doesn't mean they're right, only that they may have insights I didn't consider.)