fatwa is an Islamically legal opinion or ruling issued by an Islamic scholar....
usually when an issue does not have a ruling directly in Quran or Hadith, a scholar (or group of them) will issue a fatwa based on Quranic principles and Sunnah of the Prophet (saw)....
since the fatwa is issued for something that is not covered by Quran and Hadith, and is the opinion of a scholar, hence u can find a contradicting fatwa by another scholar who views the things from a different perspective....
and since there is not hierarchy in Islam, u cannot say whose opinion is to be given more weight, except if one is clearly much more learned than the other....
also if a fatwa has been issued by a scholar in older times, the normal practice is to uphold it, unless drastic changes in conditions call for a revision....
e.g. vaccination was not found in the time of the Prophet (saw) and the companions, and is not mentioned in the Quran so the debate came whether vaccination breaks the fast or not....
some scholars say that any intake during fast annuls the fast....
others say that if it is a necessary medicine (like insulin intake for diabetic patients) and is not a makeup for food/diet than it is allowed....
hence u will have different opinions on the matter....
^ i dont think there wud be many muslims who agree that bin laden is in any position to issue a fatwa....
he can spread his words but is he really taken as a mufti????
I will agree.....its been very correctly stated by Armughal that the person issuing the Fatwa has to be in a position where people believe in their verdict. However unfortunatley as is the case with most things in Islamic world there is no proper format no structured approach towards issuing of a Fatwa which is a very important thing....its like amending the constitution...I think what really should happen is that there should be a council that comprises of members of major sects which should have the authority of issuing a Fatwa..And it was done when a fatwa declaring suicide attacks as haram was issued in Pakistan by a committee that consisted of ulemas from all major sects in the country.... Bin ladens word definitely cannot be taken as a fatwa.....he is neither an alim nor a mufti