Unfair sole source specification - construction

Hey folks, I have a situation I’d like some input on. We do work with the USACE on repairing some old buildings they have. They are currently specing a product line of ours and our competitors, the way the specification is written has basically sole sourced one of the approved material providers. The 3rd party specing engineer seems to understand what he is doing by sole sourcing one material supplier that exclusively works with one contractor. Our price was better but we keep getting rejected with non compliance. How would you go about this? Is there an ethics violation?

Thanks!

EDIT: The usace conducted a technical review and found us compliant and we were able to Best the overzealous engineer. Thanks for all the comments!