Default encoding of Request-URI

Apologies if this question has been answered many times, but if it has been,
I can't seem to find the answer.

In RFC 2396 section 2.1 paragraph 7 it states that

"Internet protocols that
   transmit octet sequences intended to represent character sequences
   are expected to provide some way of identifying the charset used"

and

"An individual URI scheme may require a single
   charset, define a default charset, or provide a way to indicate the
   charset used."

Request-URI (Sec 5.1.2) as defined in RFC 2616 relies on constructs taken
from 2396. However it doesn't seem to state what the encoding is from octet
sequence to characters. I have seen Latin-1 and US-ASCII pop up as default
encoding schemes. If this is the case, how does one encode paths with
characters that can't be represented in these schemes?

Thanks for any help.

--
Ronan