It is enabled by a feature of the Youtube service.
They explicitly disallow downloading, but it is not enforcable (though that word probably doesn't mean what I think it means... the law probably overrules physics)
Severance
"If it turns out that a particular term of this Agreement is not enforceable for any reason, this will not affect any other terms."
You probably won't ever actually need to use that defense outside of internet arguments honestly... for all their noise the most repercussions the average person might ever see from infringing copyrights is a scary letter from an ISP.
Good luck if the legal system decides to test your hypothesis though.
This isn't about YouTube's TOS at this point, you're making a copy of a copyrighted video without the consent of the copyright holder
> downloading works protected by copyright without the authority of the copyright owner is an infringement of the copyright owner's exclusive rights of reproduction and/or distribution
Secondly, the author somehow gave permission to YouTube to make the video publicly available and downloadable, and YouTube is perfectly happy to provide to me the download URL.
Laws don't exist in a vacuum, so it doesn't seem like a stretch for my comment to refer to the laws actually applicable here right?
Your second point is just remixing the same Stallmanist POV I call out above.
YouTube doesn't just provide you with anything. You go to YouTube, and you find a link, and you stick it in your unit tests.
The fact YouTube's server replies is neither here nor there in the eyes of the law (ironically Youtube does actually return 402 "payment required" and 429 "too many requests" of they figure out what you're doing)
You're free to make whatever esoteric argument you want, but after realizing they did something as silly as put copyrighted videos in the unit tests, there's not much of a leg to stand on.
Especially when there are literally dozens of YT downloader type projects of Github still up right now that didn't do that...
The proper procedure to do so would be to sue the authors, and from what I can gather none of the core authors are in the US.
That would be an Elbakyanist stance, not a Stallmanist one.
Elbakyan doesn't hide behind these kinds of tired non-arguments and instead admits SciHub is illegal and pushes people to take action so it's not: https://engineuring.wordpress.com/2018/07/07/why-sci-hub-is-...
My apologies for not divining the tea leaves on your made up term that I guess was not meant as a bad joke, but ends up being one anyways.