Legal or not, there are real safety reasons not to put a small child up front. I bet your car's user manual says not to put kids up front. The safety systems are designed with minimum height & weight assumptions. The front seat belts aren't designed for a car seat. But most importantly, airbags explode with serious force that can break bones in a kids face. If they're in a rear facing car seat it can strike the seat (which will be close to the dashboard) with enough force to snap their spine.