Yes, and IF (God forbid) the child is killed or badly injured in a crash, you may have to face criminal charges. It is worth noting that this seat MUST be installed using the top tether strap - even in forward facing mode. If you don´t have a top tether anchorage point in your car, you cannot use the seat forward facing. the top tether point that some EU cars have have only been tested to 18 kg. this seat goes 36 kg.
If you have a top tether point in your car
If you don´t get caught with the illigal seat
You child doesn´t get injured in a crash in this seat
Then you´ll be fine