They can't. No quorum.
Actually they can. The 3/5ths qourum requirement ONLY applies to fiscal legislation. So they could go ahead with CCW / gun legislation and other non-fiscal laws.
They need 20 for a quorum only for passing fiscal legislation. If it's non-fiscal, they already have enough for a quorum.
Think of all the non-fiscal goodies they can pass while the Dems hide out in IL: make WI a right-to-work state, all kinds of pro-gun legislation, the sky's the limit. If only they had the balls....
They don't have a quorum to pass fiscal legislation, such as budget related items. They do have quorum (50%+1) to pass all other legislation.