Auctioneer Frederic Thut, who will auction the 'Banksy' on Saturday (February 23) insists that the artwork was acquired legally from the owner of the wall - but that local laws prevent him from revealing their identity.
He has accused local people of assuming moral ownership of something that is not theirs.
The owner of the wall, on which the artwork was stenciled, remains a mystery to local people in Wood Green.
Retailer Poundland, which occupies the building, is only a leaseholder. They say they do not condone the removal of the painting.
Councillor Alan Strickland says that locals see it as an act of theft:
"The feeling in the community here very strongly is that this is piece of art given freely by Banksy to our community. It belongs to our community, and we've really enjoyed having it here.
"It seems quite wrong to take that out secretively and sell it at auction in Miami for half a million dollars. That seems completely counter to the spirit with which Banksy gave it to us," he said.