I like your choice of words. Couldn't a conservative Congress pass a bill, to be signed by a conservative president, expelling specific states from the Union? My nominees for expulsion:
List 1 - everyone but Texas and a small number of other states, perhaps UT, ID, WY, OK, and others who overwhelmingly rejected Obama's socialism and who request expulsion.
List 2 - the states that gave Obama 55% or more support in 2012, when they should have known better. IL, CT, NJ, DE, ME, CA, MA, MD, RI, NY, VT, HI, and DC.
The practical effect of expulsion is equivalent to secession, but the legal status may be far prettier. Besides, I don't think the sissies on the left have the guts to fight a war just to keep us under their thumbs. The thugs on the left would be too happy to have free access to their undefended subjects in their set of states, and wouldn't bother with free and armed Americans.
Theoretically - yes. Practically - never happen. I know of a lot of southerners who would love to be on that list right about now ;')