i'm not really sure, i don't think it's a problem as long as the driver isn't drunk last month we went to the art of flight premier and on the way back we were all drinking beers in the van (except our designated driver) we got pulled over for a routine alcohol controll and the officer tested the driver, he came out clean and he just said, be careful, have a good night !
so no, i don't think it's a problem in Belgium :)