[M_a_t_t]

Cars older than 25 years are easier to import. They don't have to conform to emissions standards after they pass 25 years.

(I think) There is a requirement that any imported car must have documentation that the engine passes the requirements for that year. If the car was never sold in the U.S. it doesn't come with that certification automatically. You have to either get it from the manufacturer or get it certified yourself. Both a big hassle at least, if not impossible. Once they pass 25 years they don't have to adhere to this rule and you just have to ship it and fill out some paperwork. Again, I've never done it so this may not be 100% accurate.