What law? They locked down iPhone and law does not care. How is it different for Mac? The could've locked down their M1 Macs, but they deliberately chose not to.
I think the parent comment was refering to law(s) preventing reverse engineering of hardware - thus "Apple would prevent people reverse engineering the M1 if they could".
"locked down" from your comment as I understand it, is just making it hard to gain root on the device. Nothing in most Western law prevents you or I from jailbreaking the phone or cracking it open and looking at it under a microscope or whatever. Thats good. What would be perfect is of course publish schematics and manuals etc.
What law? They locked down iPhone and law does not care. How is it different for Mac? The could've locked down their M1 Macs, but they deliberately chose not to.