See this article: http://www.lightpanel.com/comparison/tritiumpress.htm and note the part about the $2,500 fine for improper disposal and the sentiment that the amount is too low to be effective.

There were some old CPF threads citing code sections that you missed, however the new CPF software's search function doesn't currently index old threads. I do know from experience that most vendors (including US vendors) of tritium products refuse to sell to US consumers. The exemptions are limited to specific products like wristwatches: http://www.nrc.gov/reading-rm/doc-collections/cfr/part030/part030-0015.html

Finally, those markers make some sense for portable devices, but for light switches it's cheaper and more practical to just use those translucent switches that have little neon lamps inside. Yes they stop glowing during power outages, but the lights won't be powered either, so finding the switch isn't that helpful. And exit signs should have some battery powered lighting to illuminate the way to the exit, so they don't need tritium.