The treaty, as amended by the Senate of the United States, with the accompanying papers and the evidence that in that form it had been ratified by Mexico, was received at Washington on the 4th day of July, 1848, and immediately proclaimed as the supreme law of the land. On the 6th of July I communicated to Congress the ratified treaty, with such accompanying documents as were deemed material to a full understanding of the subject, to the end that Congress might adopt the legislation necessary and proper to carry the treaty into effect. Neither the address of the commissioners, nor the reply of the President of Mexico on the occasion of their presentation, nor the memorandum of conversations embraced in the paper called a protocol, nor the correspondence now sent, were communicated, because they were not regarded as in any way material; and in this I conformed to the practice of our Government. It rarely, if ever, happens that all the correspondence, and especially the instructions to our ministers, is communicated. Copies of these papers are now transmitted, as being within the resolutions of the House calling for all such "correspondence as appertains to said treaty."
When these papers were received at Washington, peace had been restored, the first installment of three millions paid to Mexico, the blockades were raised, the City of Mexico evacuated, and our troops on their return home. The war was at an end, and the treaty, as ratified by the United States, was binding on both parties, and already executed in a great degree. In this condition of things it was not competent for the President alone, or for the President and Senate, or for the President, Senate, and House of Representatives combined, to abrogate the treaty, to annul the peace and restore a state of war, except by a solemn declaration of war.
Had the protocol varied the treaty as amended by the Senate of the United States, it would have had no binding effect.
It was obvious that the commissioners of the United States did not regard the protocol as in any degree a part of the treaty, nor as modifying or altering the treaty as amended by the Senate. They communicated it as the substance of conversations held after the Mexican Congress had ratified the treaty, and they knew that the approval of the Mexican Congress was as essential to the validity of a treaty in all its parts as the advice and consent of the Senate of the United States. They knew, too, that they had no authority to alter or modify the treaty in the form in which it had been ratified by the United States, but that, if failing to procure the ratification of the Mexican Government otherwise than with amendments, their duty, imposed by express instructions, was to ask of Mexico to send without delay a commissioner to Washington to exchange ratifications here if the amendments of the treaty proposed by Mexico, on being submitted, should be adopted by the Senate of the United States.
I was equally well satisfied that the Government of Mexico had agreed to the treaty as amended by the Senate of the United States, and did not regard the protocol as modifying, enlarging, or diminishing its terms or effect. The President of that Republic, in submitting the amended treaty to the Mexican Congress, in his message on the 8th day of May, 1848, said:
If the treaty could have been submitted to your deliberation precisely as it came from the hands of the plenipotentiaries, my satisfaction at seeing the war at last brought to an end would not have been lessened as it this day is in consequence of the modifications introduced into it by the Senate of the United States, and which have received the sanction of the President. ... At present it is sufficient for us to say to you that if in the opinion of the Government justice had not been evinced on the part of the Senate and Government of the United States in introducing such modifications, it is presumed, on the other hand, that they are not of such importance that they should set aside the treaty. I believe, on the contrary, that it ought to be ratified upon the same terms in which it has already received the sanction of the American Government. My opinion is also greatly strengthened by the fact that a new negotiation is neither expected nor considered, possible. Much less could another be brought forward upon a basis more favorable for the Republic.
The deliberations of the Mexican Congress, with no explanation before that body from the United States except the letter of the Secretary of State, resulted in the ratification of the treaty, as recommended by the President of that Republic, in the form in which it had been amended and ratified by the United States. The conversations embodied in the paper called a protocol took place after the action of the Mexican Congress was complete, and there is no reason to suppose that the Government of Mexico ever submitted the protocol to the Congress, or ever treated or regarded it as in any sense a new negotiation, or as operating any modification or change of the amended treaty. If such had been its effect, it was a nullity until approved by the Mexican Congress; and such approval was never made or intimated to the United States. In the final consummation of the ratification of the treaty by the President of Mexico no reference is made to it. On the contrary, this ratification, which was delivered to the commissioners of the United States, and is now in the State Department, contains a full and explicit recognition of the amendments of the Senate just as they had been communicated to that Government by the Secretary of State and been afterwards approved by the Mexican Congress. It declares that—
Having seen and examined the said treaty and the modifications made by the Senate of the United States of America, and having given an account thereof to the General Congress, conformably to the requirement in the fourteenth paragraph of the one hundred and tenth article of the federal constitution of these United States, that body has thought proper to approve of the said treaty, with the modifications thereto, in all their parts; and in consequence thereof, exerting the power granted to me by the constitution, I accept, ratify, and confirm the said treaty with its modifications, and promise, in the name of the Mexican Republic, to fulfill and observe it, and to cause it to be fulfilled and observed.
Upon an examination of this protocol, when it was received with the ratified treaty, I did not regard it as material or as in any way attempting to modify or change the treaty as it had been amended by the Senate of the United States.
The first explanation which it contains is: