Noted for future reference.

GateKeeper allows for individual exceptions when the user selects “Open” from the context menu on an application. Is there a way to revoke these exceptions?

Look into “sudo spctl –list –type execute” to find the relevant rule(s) and “spctl –remove –rule " to delete it/them.

https://developer.apple.com/library/mac/documentation/Security/Conceptual/CodeSigningGuide/Procedures/Procedures.html#//apple_ref/doc/uid/TP40005929-CH4-DontLinkElementID_5