They did not deny the claims of the restrictionists that slavery was ethically wrong and economically destructive, but they contended that the evil and the impolicy of it would be mitigated by allowing the slaves to be spread over a larger extent of territory, reducing thus their numerical ratio to the white population in the older Commonwealths, and enabling their masters {72} to emigrate with them from poor and exhausted lands to rich virgin soil, instead of being obliged to keep them in want, or sell them to new and, therefore, less considerate masters. They argued, upon this point, that all importation of slaves from foreign countries having been strictly prohibited, not one slave could be added to the number already existing by allowing their movement into new territory, but that their condition would be vastly improved by the increased products of their labor. [Sidenote: The pledge to maintain slave property in Louisiana in the Treaty of cession.] They contended, finally, that the treaty with France by which Louisiana was ceded to the United States contained an express provision pledging the United States Government to protect all the existing property rights of the inhabitants of the province, and to admit these inhabitants, so soon as consistent with the principles of the Constitution of the United States, to the enjoyment of Commonwealth powers on an equality with those of the other Commonwealths of the Union. There is no question that hostility to slavery colored the views of the restrictionists in regard to the constitutional powers of Congress, and there is also no question that the anxiety of the slaveholders to maintain the security of their property led them to exaggerate all of the defences of the Constitution in its behalf. It must, however, be conceded that the opponents of the restriction had, from the outset, the better of the argument in the question of constitutional law, and maintained it throughout the debate. They did not express themselves as clearly and as exactly as the political scientist of this age would do, but they demonstrated quite convincingly that the questions of political ethics and public policy were, at the moment, entirely impertinent, unless it could be satisfactorily established that Congress possessed the constitutional power to act in the {73} premises. And they showed that no federal system of government could exist, as to the new Commonwealths, if Congress had the unlimited authority to distribute powers between the general Government and these Commonwealths, which the interpretation that the restrictionists placed upon the clause of the Constitution vesting Congress with the authority to "admit new States into this Union" involved. The ethical and economical influences and considerations weighed more heavily in the minds of the Northern members than the arguments from constitutional law, although they asserted that the Constitution also was upon their side.