HTTP error response code

Scenario: App to App (no Browser)
- App1 obtains (/has) an assertion
- App1 presents the assertion to a SP App ( no browser)
- SP APP determines that the assertion is invalid (expired or ...),

At that point, does he SP app return a HTTP 200 with the right error code in the SAMLResponse.

Looking at the documents, it is not clear ... may be it is spelled somewhere  and I am missing it.

Thanks,
/Prasanta