"they could use a copy of the chip to try five different PIN codes, and then replace the chip with a fresh copy of the original and try five more"
I don't know how I could have made it any clearer that I was proposing an attack on the PIN, not the key.
>> It's encrypted, but here's the thing: the encryption key is also (almost certainly) stored in the same chip. So all the FBI needs to do is de-solder the chip, mount it in its own hardware, and read out the data.
This is not correct and was the main suggestion you made.
>> I don't know how I could have made it any clearer that I was proposing an attack on the PIN, not the key.
Because you just did. You are now claiming that an offhand comment you made that resembles what the ACLU suggests is the main point of your post and that is not the case.