This appears to be the suggested edit in question.
I wasn't one of the two users who decided to reject this edit. So I can only speculate what their motives were. But what I would find questionable about this edit is that it does more than just adding references. It changes the tone of the answer by putting words into the author's mouth which might not have been their intention.
The edit changed this sentence:
In other words someone to assess if you are fit to be entitled to something that is supposed to be a right.
In other words, someone to assess if you are fit to be entitled to something... something which is supposed to be a right!
A subtle difference, but it does change the tone of that section to sound a lot more polemic. This might conflict with the author's original intention.
An even more invasive edit is that the edit takes this paragraph:
Tests require administration from the state/government. The right to bear arms is partly to protect personal liberty from the government/state.
and then adds this to it:
be they poor people (and as such disproportionately underprivileged minorities) or anybody outside a particular social or political circle, whether buying or selling.
This is something the original author did not write and which makes implications the original author might not have wanted to make.
While we always encourage people to be bold and improve content (including cutting sections which are inappropriate), those improvements should not put words into the author's mouth. If you believe that the author could make better arguments for their points, then it is usually better to suggest to them to make certain arguments in the comments and leave the decision about whether to write those into the answer or not to them.
Then the edit added a lot of references which are interesting in themselves, but really not that relevant to the topic at hand. The question and answer are about gun legislation in the United States. But the references are all about gun legislation in the United Kingdom. Yes, the answer does mention the history of UK gun legislation in the last sentence of the last paragraph, but this appears to be kind of a secondary off-hand remark. I don't think that this one sentence which isn't really all that on-topic really justifies to add six different references. Addding that list of citations just to back up that one paragraph makes the impression that this point is a lot more important for the author than it seemed to be before, which again might conflict with the author's original intention.
Regarding the links themselves you added as references:
- The links to the domain
dvc.org.uk appear to be verbatim copies of historic laws, but if you look at the frontpage, the domain does not... well... let's just say it doesn't seem to be very politically impartial. I don't want to claim that the texts of these laws are not authentic, but it might be better to find them on a more reputable resource.
- I can't find anything wrong about linking to
legislation.gov.uk if it were relevant to the answer. But again, the topic at hand is US gun legislation, not UK gun legislation.
- I can't say anything about the validity of referencing a book I haven't read.