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?

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