2. "...No State shall, without the consent of Congress, lay any duty on tonnage, keep troops or ships of war in time of peace, enter into any agreement or compact with another State, or with a foreign power, or engage in war unless actually invaded, or in such imminent danger as will not admit of delay." The restraint on the power of the States over imports and exports is enforced by all the arguments which prove the necessity of submitting the regulation of trade to the federal councils. It is needless, therefore, to remark further on this head, than that the manner in which the restraint is qualified seems well calculated at once to secure to the States a reasonable discretion in providing for the conveniency of their imports and exports, and to the United States a reasonable check against the abuse of this discretion. The remaining particulars of this clause fall within reasonings which are either so obvious, or have been so fully developed, that they may be passed over without remark.Madison believed that giving the states the right to defend themselves from invasion had been so thoroughly discussed previously (see Federalist #43) that it wasn't worth repeating it within the discussion of Article I Section 10 Clause 3.
-PJ
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