The Congressional Budget Office finds that 60 percent of that figure — roughly $720 billion — would go toward space-based interceptors that do not yet exist as operational technology. The last time a president asked Congress to fund a missile defense architecture built on unproven space systems, it was Reagan's Strategic Defense Initiative in 1983; Congress never appropriated the full request and the program spent decades as a budget negotiation rather than a deployed shield. The constitutional question is the same now as it was then: Article I gives the power of the purse to the legislature, and a $1.2 trillion commitment to hardware that exists mainly in proposal form is precisely the kind of open-ended executive wish list that appropriations authority was designed to discipline.