The economists that advocate such a program typically say yes.

After all, the basic idea is that it would be an offer to those who are both able and willing to work. If you don't show up to work, then clearly that's pretty good evidence that you're not actually willing, hence you can be fired.

(If you are unable to work, then some other social safety net should catch you. If you are able but unwilling to work, well, opinions differ on how much society owes you in that case, and clearly this is one of the uncomfortable but important distinctions between ULW and ELR/JG...)