Under such action, the president shall order the IRS to cease taxing states for military spending, state legislatures and governors can decide what tax rate they would like to apply towards military spending.
Congress would still be constitutionally enabled to appropriate, but if they want to run the military at a deficit, this would no longer be a question where that deficit originates.
We already do this with healthcare (opt in-opt out), why not the military?
This would take some of the pressure off of the rest of government operations every time an appropriation bill is proposed, and localize a significant amount of taxation to states where opinion is highly polarized by region.
Let the states chose between tax cuts and military bloat.