Note: those CRS84, CRS83 and CRS27 codes are already implemented in Geotools for a few months.
OGC is not enforcing a latitude-longitude approach. OGC is enforcing a "as the authority said" approach, which may or may not be latitude-longitude depending on the authority.
EPSG code prior to WMS 1.3.0 are ambiguous relative to axis order. In order to avoid ambiguity, it is recommanded to use CRS:84 instead of EPSG:4326 when we want to be sure to have a (longitude,latitude) axis order, since CRS:84 definition is very clear.
Since WMS 1.3.0, EPSG:4326 is clearly defined as (latitude, longitude). See "Web Map Service" (OGC document 03-109r1) at http://www.opengeospatial.org/standards/wms
"EPSG geographic coordinate reference systems follow ISO 6709 and always list latitude before longitude." (page 9)
"EXAMPLE: EPSG:4326 refers to WGS 84 geographic latitude, then longitude. That is, in this CRS the X axis corresponds to latitude, and the Y axis to longitude." (page 10)
I admit that it doesn't tell us what to do with URN in WMS 1.1. My understanding was "as the authority said" and it was implemented like that in Geotools, but I may be wrong. I will try to send an email to Arliss for asking him if I have a chance.