this is somehow similar to the poll at
http://vcoderz.com/forum/showthread.php?t=6802
Here's my opinion:
for now, the Hezbollah's weapons are legal since:
1- Israel is still occupying our land and the government is not doing anything regarding to that subject.
2 - Other political parties are also armed. (this is the bad point and this is illegal coz they are not fighting anyone outside Lebanon).
The Hezbollah weapons will turn into an illegal weapon when we get back the occupied lands and the prisoners from Israel.
About the discussion over the shiites and what could happen in the future. It will get clearer when the above condition is achieved. So after getting the lands and prisoners, Hezbollah asks to keep the weapon, then it will be clear that there is a plan but if they hand in their weapons, then there won't be any problem!