The death penalty, as a capital punishment, has a pretty interesting role in Israeli law, Sammy. While it is in fact law in Israel, it's not exercised as much as people would think.
The question always boils down to whether capital punishment does work as a deterrent for certain levels of crime or not. I would find it rather easy to decry that any act of terrorism must always be condemned by the death penalty. Others such as political assassinations -- especially assassinating a president -- or killing police officers or people who serve the state security apparatus could easily fall into that category as well, although it does get a bit more difficult as the level of authority diminishes. Then it opens the door for the argument as to whether a certain life is more valuable than another. But for terrorists, I have no problem whatsoever sending them to the gallows pole.
In this case here with these women, it's a delicate balance and should be decided based on the weight of the evidence as to complicity in any acts of terrorism. Merely being the spouses of terrorists doesn't cut it, frankly. Guilt by association doesn't seem to be deserving of the death penalty, unless that association bears the full extent of guilty complicity.