There is no law that dictates who you can and can't be with. The half your age plus 7 rule is only spouted by either single people, or people whose own relationships are so dire that they feel the need to have some degree of control over other people's relationships.
I'm nearly 18 and I've been with my boyfriend, who is 9 years older, for a year and a half - we got a lot of hassle for it at the start, from some of my friends (they're not my friends anymore) who didn't seem to care that I was happy and he was happy, they assumed my parents would be totally against it (they're not - they love him because he looks after me, is amazing with my little brother and sister and is always helpful and polite, and not like some 17 year old boy who only wants one thing). Once that argument failed, they started calling him a paedophile. They're too stupid to realize that he can't be a paedophile by definition, and clearly they also don't understand the concept of an age of consent or the fact that as long as both parties are legal, age doesn't matter if you're at similar levels of maturity.
I had to grow up very fast and was quite mature compared to my friends thanks to my upbringing, whereas he's quite fun-loving and very funny, so we kind of meet in the middle in terms of maturity. We have lots in common - we met through a mutual hobby - and our relationship has been much more succesful and lasted longer than any of those of the people who mocked us, which I think shows just how wrong they were.
Sorry for the long story, but I think it's about time sad people with nothing better to do than create rubbish rules about relationships learned that not every case is exactly the same