Is there a way to configure a "CSP" for a desktop application?

I'm trying to find a way to block any requests to domains my app decides not to trust. I've discovered the default capabilities of App Transport Security, which is a great start, but would still allow a remote connection to a third party that uses HTTPS.

I ask this in the context of a Safari App Extension, although I'm sure this could apply to any macOS/iOS application. Web extensions (Chrome/Firefox/Edge) already provide this capability, and I'd like to secure my application accordingly.
Is there a way to configure a "CSP" for a desktop application?
 
 
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