Do you think Saddam Hussein had the same right to use WMD to save the
lives of Iraqi servicemen while fighting Iran and internal rebellion?

Actually, he did in the war against Iran; however, this absolute right
was tempered by international treaties on the laws of war which restrict
the use of poison gases in combat, to which Iraq was a signatory. He
used mustard gas, a blister agent, against Iranian forces. However, the
Hussein regime did not have the right to use nerve gas on civilians in
rebellion. Firstly, there were other, less drastic means to suppress
any demonstrations, as any competent army will use. The use of nerve
gas on Shiites and Kurds was to spread terror. Secondly, under the 1954
Geneva conventions, internal wars and their combatants also fall under
the same restrictions as international wars. The blanket prohibition
against using poison as a weapon applies. Any tribunal will be right to
try Saddam and his assistants for the use of this weapon.

Did Al-Qaeda have the same right to deliberately target civilians in their
war with the USA, specifically WTC?

No. Al-Queda is not a state and as such cannot declare war. Al-Queda
is a combination of private persons united by ideology. They don't fall
under the 1906 Hague Convention definition of legitimate combatants, nor
under the 1954 Geneva Convention extension of these rules. The United
States actions against al-Queda fall into the category of suppression of
criminals or pirates, not warfare between states. The acts of September
11 were by international law murder, not warfare.

Gregory Baker