Question: How can one do OIDC token validating using event signature?

As per title, if I create a cloudevent handler with signature of event, I do not have access to the headers to validate any OIDC token that I want to validate.

My use-case is for cross-team cross-project PubSub communication so having the OIDC token validation is a nice layer of security, it's easy to do with the http endpoint but I wanted to check if there is a way to do it via Cloudevent so I can also take advantage of the unmarshalling?