emptions of property from execution arising out of existing contracts.

233. A statute making the bills of a bank, whereof the state owns the stock, receivable in payment of all debts due the state, constitutes a contract between the state and those who receive the bills; and the state is thereby precluded from depriving the bill holders of the rights acquired under such statute, by repealing it. So too a state, upon a consideration therefor, may agree to exempt property from taxation, or to exempt it beyond a certain rate or amount, and such exemption cannot be revoked. On the other hand, if the exemption is a mere privilege, it may be revoked at any time, in the legislative discretion.

Prohibition as to Imposts, &c.

234. No state can, without the consent of Congress, lay any imposts or duties on imports or exports, except what may be absolutely necessary for executing its inspection laws; and the net produce of all duties and imposts, laid by any state on imports or exports, are for the use of the Treasury of the United States; and all such laws are subject to the revision and control of Congress.

235. While the states possess a concurrent power of taxation with the United States, there is one source of revenue which they cannot touch without the consent of Congress; that is, they cannot lay

any imposts or duties on imports or exports, except what may be absolutely necessary for executing their inspection laws. By this prohibition on the states to impose duties, and confiding the power to Congress alone, a uniform system of duties is secured, and rival systems on the part of the several states prevented.

236. For the purpose, however, of executing their inspection laws, the states may impose such duties on imports or exports as may be absolutely necessary; but the money arising therefrom is not for the use of the state. The net produce must be paid into the Treasury of the United States, and the laws imposing such duties are subject to the revision and control of Congress. Inspection laws are such as require certain commodities specified in the laws themselves, and whether produced at home or imported from abroad, to be examined, and their quality approved before they are exported or offered for domestic use.

237. A state law requiring the importer of goods, by wholesale, bale, or package, to take out a license and pay for it, under certain penalties or forfeitures for neglect or refusal, has been held by the Supreme Court to be unconstitutional and void, both because it interferes with the power of Congress to regulate commerce, and violates the prohibition which we are now considering, that no state can lay a duty on imports.

238. The Court regarded a tax on the sale of an article imported only for sale, or a tax on the thing imported, in the hands of the importer, as equivalent to a tax or duty upon imports. If such a tax could be imposed at all, it might be made so heavy as to amount to a prohibition, and thus defeat the revenue by import, so far as it is drawn from importations into the state laying the tax.

239. But when the importer has so acted upon the thing imported that it has become incorporated and mixed up with the mass of property in the country, it loses its distinctive character as an import, and becomes subject to the taxing power of the state.

Tonnage Duties, &c.

240. No state can, without the consent of Congress, lay any duty of 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.

241. By tonnage is meant the capacity or burden of a vessel expressed in tons, which is ascertained by measurement, according to a rule prescribed by an Act of Congress; and the duty, so called, is the sum levied upon such vessel after a certain rate for every ton. The states are prohibited to impose such a duty,

or any duty on a ship, without the consent of Congress, for the same general reason that they are prohibited to impose duties on imports or exports without a similar consent, namely, that there may be a uniform system in all the states: in a word, that harmony may prevail in place of diversity, inequality, and discord.

Troops and Ships of War.

242. The states are prohibited to keep troops or ships of war in time of peace, without the consent of Congress, because the power to declare war, raise and support armies, and to provide and maintain a navy, is confided to Congress, and is supposed to be adequate to the security of the states without their keeping up military armaments themselves. Besides, if the states were at liberty to keep on foot standing forces, it might lead to collisions among them or with the general government, or end in the establishment of military governments in place of civil institutions.

Compacts.

243. The restriction, that no state shall enter into any agreement or compact with another state, or with a foreign power, without the consent of Congress, is intended to prevent any infringement of the rights of the national government. The words are used in their broadest sense, and were intended to

cut off all negotiation and intercourse between the state authorities and foreign nations. They cannot, for example, without the consent of Congress, enter into any agreement or compact, express or implied, to deliver up fugitives from justice from a foreign state, who may be found within their limits.

244. Coupled with the previous clause, which prohibits any state from entering into any treaty, alliance, or confederation, the door is closed against any political or other arrangements and combinations, on the part of the states, which might interfere with the stability and harmony of the Union, or the rights, and controlling authority of the government of the Union. The consent of Congress, however, to agreements between states need not be express, but may be implied from its legislation on the subject.

Prohibition as to War.

245. The power of declaring war being confided to Congress, it is very proper that the states should be prohibited to engage in it without the consent of Congress, unless actually invaded, or in such imminent danger as will not admit of delay. Otherwise all the states might become involved in war in consequence of the folly, caprice, or rashness of any single state. When actually invaded, or in such imminent danger as will not admit of delay, the