If you are old enough to remember VHS, there was a video called, "I Am Only a Bill". It was a civic lesson on how a bill becomes a law. In fact, just last week CNN featured it during the government shutdown. It is a straightforward and candid little video. It points out that it is not easy to go from an idea to a law. Why do I bring this up? The people opposed to the CRPD are concerned that even if the ratification resolution that comes out of the Senate has reservations, understandings, and declarations that address their issues in a way they like, that future Senates could undo what they like. Well, that is true, but the same could be said for anything that the Senate passes.
The House of Representatives does not deal with treaties.
Here's the process that would be required to change a treaty that has already been ratified.
1. A Senator or Senators would draft a resolution to change the treaty. It could be their idea, the President could suggest it, or the Supreme Court could have rendered a decision that said part of a ratified treaty was unconstitutional.
2. The new resolution idea would be referred to the Senate Foreign Relations Committee. The committee would hold a hearing or hearings. The resolution may be handled by a subcommittee.
3. If a resolution is handled by a subcommittee, after hearings, the subcommittee would hold a mark up, where amendments to the resolution could be offered.
4. If a majority of the subcommittee votes for the amended resolution, it would then be considered by the full Senate Committee on Foreign Relations, which could amend it further.
5. The committee would write a report on the treaty containing the treaty, the resolution as amended, and testimony.
6. If a majority of the full committee voted for it, the resolution would be put on the Senate calendar. Usually resolutions to ratify a treaty or amend a ratified treaty are not put on the Senate calendar until or unless the Senate Majority Leader is assured it would pass by the required minimum of 67 votes.
7. The President may elect to sign or not sign the resolution to ratify the Senate sends him or her.
The process I just described can take a very long time and in fact a second swipe at a treaty already ratified may NEVER happen. Therefore, it makes sense, for those who object to certain things in a treaty being considered for the first time, to work with others to develop reservations, understandings, and declarations that address their concerns.