To expand a little more, you'd have to be in the sketch mode (sketcher application) to do so.
Outside of the sketch, (modeling application), it would probably be treated as a feature, and your best bet might be to redefine the datums associated to the sketch (reattach the sketch to a different set of datums). There's probably more than one way to do this.
Sketches, regardless of their TRUE plane location are typically XY (flat, no Z) when the sketch mode is activated....or horizontal/vertical...you might want to elaborate a bit to avoid any confusion.
Tim Flater
Senior Designer