Background
For a very long time, amendments have not been possible in the GA. As this post in the GA rules thread explains: (emphasis mine)
Amendments / repeals had been a sore point for players since the beginning of the game, and UN Mod Enodia had to formulate a rule making both illegal, since the only way to implement them was for the admins to make adjustments to the code with the passage of each game-altering amendment. Their response? "No way, Jose."
The admins worked long and hard on finding a way to address the problem of permanent UN resolutions. They decided that the amendment process was simply too difficult to code effectively, so they went with the repeal code and the strikeout of the prior resolution. Frankly, none of our current admins have the time or inclination to revisit that code, and the problem with amendments is just as difficult now as it was then. That door probably won't ever be reopened.
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Now, multiply those effects times all the passed resolutions, and correctly anticipate the possible phrasing choices that will be used in all the unwritten proposals yet to hit the floor. Write some code to address all those potential changes. Incorporate it into a simple game where the actual mechanical effects are hidden from the players, so they can't know what the effects really are. Are you starting to see the problem yet?
Similarly, "repeal and replace" as a single resolution is not possible as the resolution would have to have the stat effects of the repeal + the new resolution at the same time. All these issues stem from the fact that the stat effect of GA resolutions is entirely tied to their Category and Strength/Area of Effect. But this is changing. The new system will have Issues Editors reading the text of every proposal and coding appropriate statistical effects. This essentially removes the above argument against amendments.
So, in 2025 (or whenever the GA stats change comes into effect), will some form of amendments become a realistic idea?
Proposal 1. "Repeal and Replace"
One of the problems faced in the GA is that the only way to make changes in an existing resolution (other than pure additions) is to repeal it entirely and pass a new resolution. This unnecessarily requires two separate votes, campaigns and so on taking up more time. If authors could propose a repeal together with the replacement in the same resolution, it would allow authors to present their replacement at the same time as their repeal, and to have the resolution repealed only if both parts gain support. It is possible that this might generate political expectations for repeal authors to either show a case why the resolution does not need replacement, or propose a replacement together with the repeal. But, of course, the separate method will still be available.
Mechanically this would be pretty simple. The only change needed would be giving repeals their own (manually-coded) stat effects just like non-repeal resolutions, and allowing them to have a custom title (retaining the automatic sentence in the text that notes the repeal). After that, the GA proposal rules would have to be changed to allow new legislation in repeals. Once this is done, the "repeal" category could simply be renamed "repeal-and-replace" (or a separate category added if necessary).
Proposal 2. Multi-resolution repeal and replace
As an extension to proposal 1, this would allow more than one (indeed, zero or more) existing resolutions to be repealed in a single resolution. In that case, authors could freely combine repealing existing resolutions (or not) with new legislation (or not) as needed using one single type of resolution -- the distinction between new resolutions and repeals would be gone. This would basically be a full-fledged amendment system without all the textual complexity issues of allowing amendments of extant resolutions. This would be useful if, for instance, someone wants to make a new comprehensive resolution on abortion, a topic covered by multiple resolutions at present where repealing any one of them individually would be politically unpalatable.
This would probably be more technically complex. There would have to be a way to select more than one resolution to repeal, and the automatic sentence about repealing would have to have multiple resolutions. And, of course, the creaking old WA code would have to be taught that a single resolution can cause the repeal of more than one extant resolution.
Proposal 3. Amendment
This is the most complicated but most flexible proposal. Essentially, amendment resolutions would consist of one section for the rationale, followed by any new legislation to be made, followed by changes to an existing resolution. The latter could perhaps be implemented by asking the author to paste in the amended text of the target, and displaying something similar to a diff in the proposal page so that voters can see what the proposed changes are. Again this could be extended to multiple resolutions (if it wasn't already complicated enough!)
I am not particularly in favour of this option, because it would be pretty complicated and result in tangled messes of resolutions and amendments on amendments. It likely would also result in a lot of minor changes getting amendment proposals and wasting GA time. Personally, I prefer proposal 2 which achieves the same effect but much more simply.
What about the SC?
Repeal-and-replacing or amending Commend/Condemn/Liberate/Injunct resolution doesn't make much sense since all that could be amended would be the rationale. But Declarations could conceivably benefit. I don't know enough about SC dynamics to comment much about it.