I am not from the US nor am I a lawyer but what were his rights in such a situation? Could he have decided not to hand over the device immediately and ask for

I am not from the US nor am I a lawyer but what were his rights in such a situation? Could he have decided not to hand over the device immediately and ask for proof of ownership and ask to see a warrant or whatever-else is needed for the FBI to track him? Feds telling him "you don't need a lawyer, you are boring" sounds a lot like they actually did something incriminating, he caught them and now they are worried about legal actions against them. This seems to fit with the threatening to get the device back - no device, no evidence, no case in court, government will deny knowledge. When the feds or the police come knocking on your door, do you have the right to NOT let them inside without a warrant? Do you have the right not to answer any questions and immediately get legal help, thus creating legal documents which might serve as evidence later on? Really, what rights and freedom do you people in the USA have against the "terrorism" witch hunt or do the feds practically have "carte blanche" now?