The people of the States had sacrificed or agreed to hold in abeyance some sovereignty. To wit (emphasis added):
XIII.
Every State shall abide by the determination of the United States in Congress assembled, on all questions which by this confederation are submitted to them. And the Articles of this Confederation shall be inviolably observed by every State, and the Union shall be perpetual; nor shall any alteration at any time hereafter be made in any of them; unless such alteration be agreed to in a Congress of the United States, and be afterwards confirmed by the legislatures of every State. (This is the part that subsequently led to the Constitution.)
And Whereas it hath pleased the Great Governor of the World to incline the hearts of the legislatures we respectively represent in Congress, to approve of, and to authorize us to ratify the said Articles of Confederation and perpetual Union. Know Ye that we the undersigned delegates, by virtue of the power and authority to us given for that purpose, do by these presents, in the name and in behalf of our respective constituents, fully and entirely ratify and confirm each and every of the said Articles of Confederation and perpetual Union, and all and singular the matters and things therein contained: And we do further solemnly plight and engage the faith of our respective constituents, that they shall abide by the determinations of the United States in Congress assembled, on all questions, which by the said Confederation are submitted to them. And that the Articles thereof shall be inviolably observed by the States we respectively represent, and that the Union shall be perpetual.
In Witness whereof we have hereunto set our hands in Congress. Done at Philadelphia in the State of Pennsylvania the ninth day of July in the Year of our Lord One Thousand Seven Hundred and Seventy-Eight, and in the Third Year of the independence of America.
Agreed to by Congress 15 November 1777 In force after ratification by Maryland, 1 March 1781
Forgive me, but the Articles of Confederation were replaced by the Constitution - not amended as the convention was directed to perform. The state of Rhode Island and Providence Plantations refused to even send a delegate - which according to Article XIII cited above rendered the convention illegal. Delegates from New York and other states left the convention once the learned that it was not to strengthen the Articles. Yet the founders allowed that once 9 states ratified the new Constitution a new government was formed. In Federalist No. 43, James Madison wrote, "[o]n what principle the Confederation, which stands in the solemn form of a compact among the States, can be superseded without the unanimous consent of the parties to it?" His response:
"The first question is answered at once by recurring to the absolute necessity of the case; to the great principle of self-preservation; to the transcendent law of nature and of nature's God, which declares that the safety and happiness of society are the objects at which all political institutions aim, and to which all such institutions must be sacrificed."He also added this statement, "[A] breach, committed by either of the parties, absolves the others, and authorizes them, if they please, to pronounce the compact violated and void."
Secondly, the Articles did include the word "perpetual", not once but 5 separate occaisions. Have you ever thought about why it was purposely omitted from the Constitution? The Constitution was not meant to be "perpetual". Madison and Hamilton both referred to the new government as "experiments". Both referred to various national and state governments as experiments, more than 30 times in the Federalist Papers.
Regarding sovereignty, three states expressly reserved the right to resume the powers of self-government as a condition to ratifictaion - New York ("[t]hat the Powers of Government may be reassumed by the People, whensoever it shall become necessary to their Happiness"), Virgina ("the powers granted under the Constitution being derived from the People of the United States may be resumed by them") and Rhode Island ("[t]hat the powers of government may be reassumed by the people, whensoever it shall become necessary to their happiness"). North Carolina and Rhode Island and Providence Planatations refused to ratify until the Bill of Rights had been submitted for ratification.
The Articles are not binding, the states did retain their sovereignty that had not been delegated, and did reserve the right to withdraw from the union.