I got several airbnb gift card for a gift and now my account is restricted

Was given several gift cards for a gift and am using them on my vacation. I got a message from airbnb stating that they think I may have bought them and it is prohibited to transfer gift cards for money. They say that they may freeze my reservations and are reversing unused funds if I don't manually pay for my reservations again with a credit card? How can they do this? Any advice? Is it legal?