I also don't think a teacher is required, especially not for keeping the precepts!
However, I have found teachers at times to be indispensable. This is especially true in the beginning. A beginning meditation student is facing not only a lifetime of unwholesome habits, but a world which tosses many obstacles at you. It is like we're drunk, asleep, and in the middle of a dream. It is easier if you work with some one who is more awake.
I spent a while doing phone retreats with Shinzen Young. Some teachers are available even if you are far away.