Um, the iPhone’s screen will be covered with the fingerprint that unlocks it - I would guess that 99% of owners would use the thumb or index finger of his dominant hand as his security print.
A guy in Japan (of course) has already shown you can use a nipple to lock and unlock an iphone.
No matter what, it is still better than no unlock code like the vast majority of people.
Really, very few need to worry about the government, most just need to worry about some random purse snatcher or an unethical person who finds a phone lost in a taxi.