No, you are not allowed to do that (data types are types, not data). Instead you can do the following:
data HTTPStatus = HTTPStatus Int String
badRequest, notAuthorized, notFound :: HTTPStatus
badRequest = HTTPStatus 400 "Bad Request"
notAuthorized = HTTPStatus 401 "Not Authorized"
notFound = HTTPStatus 404 "Not Found"
or, similar:
data HTTPStatus = BadRequest | NotFound
code :: HTTPStatus -> Int
code BadRequest = 400
code NotFound = 404
message :: HTTPStatus -> String
message BadRequest = "Bad Request"
message NotFound = "Not Found"