How and why does a hybrid car manufacturer get away with false advertising on gas mileage?

The Honda Civic hybrid (2015) does NOT get the gas mileage advertised, so far. While it advertises mileage of 44 city/47 highway (45 average) the fact is so far I'd be lucky if it breaks 35 average, and has only gotten up to about 30 at most in the two weeks I've owned it and driven it in a variety of traffic conditions - both city and highway. Seems to me I may have been bamboozled, but how does Honda get away with it?

Added (1). I never wrote anything about a contract! I mentioned advertising (false advertising, to be exact), such as the window sticker, which I still have and looked at today! What am I supposed to do, drive 10 mph under the speed limit to get the mileage?

What is this, speed dating for cars? You know *nothing* after a mere two weeks. And if you believe that a carmaker is contractually obligated to give you so many MPG, you know *less* than nothing.

Windowphobe is probably hired by Honda to say good things about them! Fact of the matter is they should be posting real-world mileage based on real-world conditions, not driving like a grandma in zero traffic! We should band together against Honda in a class action lawsuit!

Honda's hybrids have been garbage from the beginning. The Insight was a huge flop because it failed to deliver on fuel consumption figures. You ought to have done your research. There have been lawsuits over fuel consumption numbers that are way off. See if someone else has already scored a victory and piggy back on it. I remember hearing about a lawsuit regarding the Insight's real world mpg numbers. The irony is my 91 Civic is can easily hit mid 30s mpg numbers without all this "technology" - more like uselsss dead weight.