Carrying a Load on a Bicycle
Evia asked: Is it against the law to have a milk crate attached to bike so you can carry groceries?
The only law that might apply is in this post:
I believe that a crate firmly attached to the rear rack of a bicycle would become a part of the bicycle and not subject to load questions. It would certainly seem safer to carry groceries in such a crate attached to a rack over the rear wheel than to carry a bag with your hand on the handlebar, which presents stability problems, as would any load on the handlebar.