When can I return a Bad Request?

The 400 (Bad Request) status code indicates that the server cannot or will not process the request due to something that is perceived to be a client error (e.g., malformed request syntax, invalid request message framing, or deceptive request routing). A business rule doesn’t fall under any of those three examples.

For More Information Please Refer: https://softwareengineering.stackexchange.com/questions/329229/should-i-return-an-http-400-bad-request-status-if-a-parameter-is-syntactically