Working with Javascript off != accessibility. Most screenreaders (the common face of accessibility technology) run on top of regular browsers, so your JS experience needs to be accessible too if you are legally mandated to (or even better if you care).
If javascript being off makes your site not work, or not viewable at least, then that's the very definition of not being accessible (i'm not limiting 'accessible' to only mean 'available to people with disabilities' like you appear to be)
Edit: Graceful degradation should be a tenet of web development. Having no provision for a person who doesn't have javascript enabled seems bizarre to me, and being bullish about the requirement seems even more bizarre...maybe i'm just getting cranky with age or something.
That is like saying that I must make sure my programs work for people who don't have a computer and rely on anotated screenshots being sent back and forth. To my programmer brain, that is just stupid.
It is one thing if we were talking about a webpage ala 1995 for joes autoshop. At most it will have a comment field (or, the horror, a guestbook) and each url will map logically to a specific public part of the site. Most likely there will be no concept of users at all.
The same thing goes for a blog although you won't get the auto updating twitter feed and, if the blog uses diques, you may have to click a couple of links to see them.
But a webapp is more like Google writer. It just lose all meaning to make it work without Javascript.
Accessibility cuts both ways, though. Choosing to prioritize the HTML-only version decreases accessibility to people who have limited bandwidth or download speeds.
This surely hasn't been a major problem since probably the 14.4k modem stages for typical sites, and, even if it was, wouldn't limit accessibility (except in the sense that it'd delay viewing by a few milliseconds->seconds). Especially when the majority of the bandwidth cost will be data that has to be sent regardless (maybe with a necessarily increased amount of metadata).
There is (thankfully) no law which say that your service must be usable for people who turn javascript of.