When you enter the US, you have to claim your checked baggage as part of the process of going through customs, then re-check your bags if you’re continuing on a domestic flight.
If you have a device in your checked bag:
you’re violating the safety rule about not having lithium batteries in checked luggage.
if you’re asked if you are travelling with a phone and you lie and say you don’t have one, then if they search your bags and find it, then they’ll have strong evidence that you lied to a federal officer, which is a crime.
You’re allowed to have devices with lithium batteries in checked bags.
When portable electronic devices powered by lithium batteries
are in checked baggage, they must be completely powered off and protected to prevent unintentional activation or damage. Electronic devices capable of generating extreme heat, heating elements must be isolated which could cause a fire if activated, by removal of the heating element, battery or other components.
American Airlines will ask you to remove devices from your checked bags is you tell them that you have batteries in your checked bags. Airlines are allowed to have more strict rules than what the FAA allows.
Sure, airlines can have whatever policies, but while not adhering to them might get you into trouble with the airline, it’s not a legal issue. The TSA doesn’t get powers from that to do anything that they weren’t allowed to do otherwise.
Now, they might lie to you to get you to give them more than they’re entitled to, but that’s a different issue.
Would it help to have electronics, phone included, in your checked baggage?
If not, then people might have to consider smuggling their phone through in a brick of coke. Or put it in a condom and swallow it.
When you enter the US, you have to claim your checked baggage as part of the process of going through customs, then re-check your bags if you’re continuing on a domestic flight.
If you have a device in your checked bag:
you’re violating the safety rule about not having lithium batteries in checked luggage.
if you’re asked if you are travelling with a phone and you lie and say you don’t have one, then if they search your bags and find it, then they’ll have strong evidence that you lied to a federal officer, which is a crime.
You’re allowed to have devices with lithium batteries in checked bags.
https://www.faa.gov/hazmat/packsafe/printable-chart
American Airlines will ask you to remove devices from your checked bags is you tell them that you have batteries in your checked bags. Airlines are allowed to have more strict rules than what the FAA allows.
https://www.aa.com/i18n/travel-info/baggage/restricted-items.jsp
Sure, airlines can have whatever policies, but while not adhering to them might get you into trouble with the airline, it’s not a legal issue. The TSA doesn’t get powers from that to do anything that they weren’t allowed to do otherwise.
Now, they might lie to you to get you to give them more than they’re entitled to, but that’s a different issue.