Well, there were several ways. It really depended on what spell it was. He raised both hands. "Well, it seems to me that the most obvious answer is to use a counterspell. Such as Lumos being countered by Nox. Finite or Finite Incantatem will likely work for simpler spells, I doubt they would even touch something Dark like an Unforgiveable, though." Except those weren't strictly speaking charms, but it got the point across.

"I suppose if you just walked into a room and saw a clearly charmed object, you may not know what the original spell's incantation was, either because it was invented or you just can't figure it out for some reason. Then you may have to use a series of spells to counteract the effects of the original charm? I dunno, I've never thought about that situation before now." He doubted that's where Schirmer was headed, but it popped into his thoughts, so he may as well address it, right?