A very Apple-style presentation which was a little hard to find: Craig Federighi talking at the Web Summit conference in Portugal. Apparently Europe is proposing a Digital Markets Act which would require mobile platforms to allow native app installations from anywhere (whereas iPhone and iPad have only ever allowed app installations from their own curated App Store).
Federighi opposes the law. This little segment is the most concise version of Apple's thinking I've seen on this, including direct responses to some common counterpoints ("why wouldn't Apple allow a special setting for people who know what they're getting into?", et cetera).