Bringing someone elses car to US?

My nephew is being offered a car from a friend so that he can have one in the US while studying in Buffalo. He would be bringing the car from Ontario. The friend says that she will insure him as a secondary driver on the car and that would allow him to take it into the US and use it while attending college in Buffalo. Are there any legal issues around this? US Custom issues? Insurance coverage issues?

You can't have a car in the US for more than a year without formally importing it and the State may have issues with him driving a car not registered in the State for a lengthy period, you need to check State law for that one. Because he doesn't own it, he can't formally import it.