The Constitution quite clearly states that spending bills are to originate in the House. So, if the House originates a spending bill that does not include funding for ObamaCare, that is completely within their power to do.
It is then NOT the Republicans shutting down government - it would be the Democrats in the Senate by voting down the bill / amending it to re-instate the spending, or by Obama himself vetoing a bill without that funding who would be shutting down government.
All because of Obama's intransigence regarding negotiating with the House Republicans.
Knowledgeable people recognize that the party which is unwilling to negotiate is the one which is the problem, not the one who wants to negotiate.
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Sorry, but none of that spending is mantatory in the least. Social Security is a largesse conferred on the people by the government which can be ended at any time the government so chooses. Same with everything else. Nobody has a right to government money.
Can you cite the specific rulings or legislation which created this law?
Can you understand that I am not willing to take YOUR word for it?