COPY statement cannot take binding parameters

Trying to parse and bind the following:
  COPY (SELECT $1::INT) TO STDOUT

gives a correct parsing-done, but then in the parameterdescription tells
me that there are no parameters.

Is this intended?
Is this a limitation of the COPY statement that will not change?
In that case, might I suggest the server generates an appropriate error
message when someone attempts to do this?
-- 
Sincerely,          Stephen R. van den Berg.
"Having a non-smoking section in a restaurant is likehaving a non-peeing section in a pool."