It is rather interesting to me that many of the top figures in the PLO are calling for Abbas's release. What is there motivation? What do they see they can gain from his release? What could they gain from asking that a known terrorist be given immunity?

The claim that Oslo legally gives Abbas immunity is a bit of a stretch. Read the Oslo Accords. The section dealing with immunity says this:

Palestinians from abroad whose entry into the West Bank and the Gaza Strip is approved pursuant to this Agreement, and to whom the provisions of this Article are applicable, will not be prosecuted for offenses committed prior to September 13, 1993.

Abbas, I understand, was allowed to enter the West Bank a number of years ago. But who ever wrote those left it too open -- one of the many problems of documents between Israelis and Arabs.

But given that this is an accord between Israel and the PLO, it is a reasonable interpretation to think that the prosecuter in question here would be Israel. After all, it wouldn't be reasonable to think that some Palestinian who detectives just recently found to be responsible for a (non-terror related) murder in Romania in August 1993 couldn't be tried for his crime in Romania.

Certainly, Oslo says that Israel can't prosecute Abbas, but it doesn't say that Italy or the US can't. The fact that the US was a witness to the Oslo Accords is a rather weak legal basis for saying that the US must release Abbas.

Which brings me back to my original question. Why argue for this guys release on such flimsy legal reasoning?