There is no law against boys wearing girl clothes. The problem is that scoiety looks down on boys who dress in girls clothes. More and more clothes are being desinged and manufactured so they can be worn by either boys or girls. Also a good number of boys, particularly in their early teens, do wear girls jeans because they fit better and are more comfortable. The boys just make certain the jeans do not have any decorations that show off that they are girls jeans.