Maybe. On the other hand, sufficiently powerful beings are not contained by normal circles--Harry mentions it when he's discussing the super-circle in Fool Moon.
It's a solid steel ring, and the whispers Harry is hearing cut off when he empowers it. That seems to me to make it clear that Harry was able to cut it off.
Besides, again, the coin itself is a prison meant to keep the Fallen from affecting the outside world.
The coins kick off the game when picked up by putting a shadow in the mind of the one who picked it up. Clearly the Fallen don't need consent to operate at some level.
Sure it does. Harry picked up the coin willingly, right? And WOJ is that Harry didn't just put his booted foot down over it because on some level, he
did want the power it offered.
And note that Lash keeps urging Harry to
willingly take up the coin properly. Harry has to
actively make a decision to use the coin's power.
Why do you think they needed to torture Marcone and Ivy to get them to take a coin? Because they have to willingly pick it up. You apparently can't force it on someone.