The seat belt buckles and unbuckles with ease, but it's also childproof. 

To buckle: 

First, straighten out straps. Then, connect the clasp so that the left side rests on top of the right side. Click the connected clasp into the buckle. 

To unbuckle: 

Push the "Lalo" button in the middle of the buckle and pull straps apart. Voila!