HTTP Error code for faults (part3, sec 3.7)

3.7.1 says:
<<<
For every Interface Fault component contained in an Interface component, 
an HTTP error code MAY be defined. It represents the error code that will 
be used by the service in case the fault needs to be returned.
>>>

Would it be possible to add that fault definition SHOULD NOT go against 
the definition of the HTTP error codes?
Ie: you may specify returning an error code using 4xx if the error is in 
the HTTP request, a 5xx error for a "server-side" error during the 
processing of the request, and preclude the use of 3xx for faults?
Or reference RFC 3205 Section 8 [1].
Thanks,

[1] http://ietf.org/rfc/rfc3205.txt

-- 
Yves Lafon - W3C
"Baroula que barouleras, au tiéu toujou t'entourneras."