Peter Duniho wrote:

He's not obligated to cancel the "VFR on
top" clearance, as far as I know.

Ah, I'd not thought about it that way. It's not a comforting thought: that
I could be above a ceiling and unable to return to full IFR. There's no
regulatory requirement that would force a controller to let a VFR-on-top-er
back into the system?

- Andrew