The laws of physics are not anti-competitive. What would be an anti-trust issue is if Walmart took steps to prevent their customers from shopping at Costco.
Apple is stopping iPhone owners from going to the equivalent of Costco by banning competing app stores. That's a pretty clear violation of U.S. antitrust laws.
Apple is not preventing you from choosing to buy an Android phone.
Owning an iPhone is like being in a Walmart. You can either buy from the store or go somewhere else. Walmart-made products will be cheaper in the store. You can always go somewhere else. You can make the choice on whether you want to go to Walmart or Costco before, during, or after your stint in either.
They're preventing you from buying iOS apps from anyone but Apple.
>Owning an iPhone is like being in a Walmart. You can either buy from the store or go somewhere else.
It's not and you can't. There's nothing inherent that forces you to only buy software from Apple because you own an Apple device. And you can't go somewhere else to buy your software because Apple blocks that.