Should we expand this section of the tag schema? E.g., Is following the flow of traffic a valid speeding defence in Texas? was initially tagged with prima-facie-speed-limit. I thought that was two levels too far given the current schema. Any opinions on that?
I don't see why it hurts to have such tags.
The site is still quite new, and is still in beta; at the time the question was created, there was not a prima-facie tag, either, but that's not a good excuse not to have such tag (especially since we've passed the private beta stage where any user can create a tag, now one needs at least 150 rep).
In the case of speeding, the defences available for absolute and prima facie speed limits are entirely different -- those that are applicable to absolute limits could also be used for prima-facie ones, but not the other way around.
So, you may ask, why not have an absolute limit tag, too? Well, that's because absolute is rather the default speeding charge, applicable to all speed limit jurisdictions, and non-regulars cannot be expected to use such a tag by themselves, so, the tag would rarely be used. Prima facie speed limits one, on the other hand, would be quite useful to group those issues that are unique to the 13 of the 52 jurisdictions in the US that do have prima facie speed limits, as per http://www.mit.edu/~jfc/laws.html (39 absolute, 10 mixed, 3 prima facie).