US here, got issued a chipped card about a year ago and noticed quickly that any attempt to swipe with my card would be greeted with an error message and instructions to insert the chip. For all systems I've seen, it seems that if the merchant accepts chips and if the card has a chip, the chip must be used, regardless of any user reluctance.
Most readers I have experimented with in the US will allow a swipe after 3 unsuccesful chip reads (inserting card in opposite direction w/ chip exposed).