Can a child, 18 or under, publish a written work through a publishing company?

I went to a popular free publishing company (PublishAmerica) and they state that, legally, any one under 18 cannot publish a book. On this site people have answered "your parents are just in charge of your contracts" or "If your parents do it for you" but they state that only the author can sign the contract. Therefore, I am in a bind. And I know they are correct so far because they use the correct legal system and have evidence, and I don't see any of the answers here have evidence. So does anyone know a loophole to this or any other sites that will publish my book (for free mind you) with a loophole in the said law. Thanks for any help you guys can give me.