One of our resident attorneys would have to verify this, but I would think that this action would form the basis for one whopping big lawsuit by the taxpayers of the other states that are required to pony up to pay this bribe to Nebraska.........particularly involving Medicaid, which all states are required to provide.
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Conceptually, there are real "Equal protection of the laws" issues with it, IMHO. It does depend on how it is actually worded though; legislative bodies at all levels have great track records for crafting language so it reads like there are neutral criteria, but in fact it only fits one group. Also it can't be taken to court until it makes in into a final bill that becomes law, and even then the Federal courts are loath to venture into this.
Any Federal or military construction or other activity is going to selectively benefit some states over others, and logically only states with ports benefit from harbor work, etc. But this kind of national entitlement program is a whole different situation. It remains to be seen if anyone will want to invest in the fight, though.