This question already has an answer here:
Negotiations over the current US government shutdown have, as far as I've heard, mainly been between the President and Congressional Democrats. So far, Republicans in Congress seem to be siding with the President in refusing any agreement not including a border wall, but there seem to be some cracks in this.
Suppose that a sufficient number of Congressional Republicans decided to break with the President and reached an agreement with Democrats, but which the President still found unacceptable. As I understand it, both houses of Congress could pass a spending bill along those lines. The President might then veto it (he could stall for up to 10 days first). Suppose, however, that Congress had the votes to override the veto (2/3 of each house).
If they were to override his veto, would this end the shutdown, or would the President somehow be able to continue it anyway?
I wonder if there is any argument that, even if Congress allocates money for the Government, it is up to the President to decide whether to actually spend it.