Stuart Pearce wrote about it in more detail in his book, apparently the original hair ruffling incident happened few weeks before the Hillsborough tragedy when laws made a mistake in a league game leading to Lipoool scoring, in the replay to the semi at old Trafford Aldo went out of his way to find Laws and apologise, saying the last few weeks had put everything into perspective and he regretted doing it etc, Laws accepted the apology and that was the end of the matter.
Until an hour later when Laws scored an OG and good old Aldo done the exact same again. Lovely fella.