Yes, Congress legislated the ground rules.
And what Congress and the Executive give, they can also take away. And would the SCOTUS be involved?
Thanks for the research, Publius, but I don't think it's as benign as you might believe.
Congress addressed this issue because of the court case surrounding the 27th Amendment, and SCOTUS agreed. Here is how it unfolded.
The 27th Amendment was proposed by Madison in 1789 along with 11 other amendment proposals. All 12 proposals were slam-dunked through Congress, and 10 of them were ratified immediately and are known as the Bill of Rights. Two others languished in the ratification phase.
In 1984, an aide to a Texas state senator was engaged in research on amendment propsals that had been passed by Congress but had not received enough ratifications to get into the Constitution. He discovered Madison's 12th proposed amendment, quit his job and held seminars for state legislators across the country about it. Ratifications began to pile up, and the 38th ratifrication hit the desk of the Archivist of the United States in 1992. Mr. Remini sent a memorandum to Congress that its power to grant pay raises had just been curbed by a new amendment to the Constitution. Congress went ballistic.
Congress sued the Archivist demanding that the 27th Amndment be removed from the Constitution on the grounds that the ratifications were not contemporaneous, i.e., the ratifications of the 1790's were "stale" and had to be done over. The federal court rejected the arguments and told Congress the only way it could get the 27th removed was through an amendment repealing it. The court, however, informed Congress that it could legislate and reform the amendatory process provided it did not contravene the clear language of Article V.
Congress appealed to the DC Curcuit and was shot down without comment. Congress appealed to SCOTUS, which refused to take the case.
Congress legislated a blanket 7 year timeline for ratifications for all future amendments. Then Orrin Hatch stepped in.
In my essay, I poined out that the ABA did a study on an Article V Convention in 1965. Sen. Everett Dirksen (R-IL) turned that study into a bill in 1968 because the move for an Article V Convention to repeal the SCOTUS "One Man/One Vote" decision had hit 32 states. It never hit 34, and Dirksen died in 1969.
Sen. Sam Ervin (D-NC) picked up Dirksen's fallen torch and introduced the bill every session to no avail. When Ervin retired, Hatch had picked it up. Hatch added his bill to the amendatory process reform bill, and it was enacted in 1992.
The 32 requests for an Article V Convention for a balanced budget amendment pre-date the 1992 bill, so they are considered immune to the 7 year shelf life rule in the law and are thus still valid. If 2 more states sign on, there will be a convention, but only to address a balanced budget amendment. This is due to the Principle of Agency, a basic principle of jurisprudence. The convention is an agent of the states, and thus cannot go outside the purview granted it by the petitions from the states.
In 1789 two states asked for a general convention to address all possible subjects, i.e., an open convention. Those two petitions are still on the record, but before an open convention could be called by Congress, you would need 32 more states to pile on to those two old petitions. That won't happen unless there is a general catastophe involving government, and the states want to drastically curtail the federal government. It's a constitutional nuclear weapon, but it's not a stealth weapon.
Congress, by the way, cannot take an Article V Convention mandated by the states to address a balanced budget amendment, and permit it to handle any other topic, much less let it become an open convention addressing anything. The Principle of Agency stands in the way, and overturning 800 years of Anglo-American jurisprudence going back to the Magna Carta won't fly under any circumstances.