Friends son receives SSI for autism but my friend uses a lot of it on himself

So my buddy has a kid who has autism and receives around $740 a month. My buddy uses that for drugs,shoes, and alcohol for himself. How is this legal? Is there anything that can be done. He is a terrible parent who only cares about getting that money and he gets it on the 1st of every month and it's gone a few days or a week later.