They may not be able to "defund", but they can pass legislation that prohibits any funds, regardless of the source, be spent for those purposes. That would also prevent Obama from moving money around to pay for it.
So rather than worrying about "shutting down the government" by withholding funding for a specific department, they should pass a short-term CR, but have a clause in the bill to prohibit any money be spent by any department or agency of the US government to provide work permits or take any other actions to implement the steps laid out by Obama last night. Now Obama could veto it, but he could not credibly claim that the GOP was "shutting down the government", since the bill would contain funding for all legitimate government functions - it would just contain restrictions on how that money could be spent.
Of course, it would be up to the GOP to make the case to the people that Obama would rather refuse to fund the government than allow any restrictions on his amnesty plan. And based on recent history, the ability of the GOP leadership to communicate even a simple message like that is doubtful.
RE: they can pass legislation that prohibits any funds, regardless of the source, be spent for those purposes.
Yes, and I’m sure Obama will sign that legislation into law ( HA HA HA ).
That sums it up rather nicely.