Whose going to make them sign?
But that aside. I had not formed an opinion on it when I started the thread, but it might be wise to make Israel a party to the NPT as a nuclear weapons state. IF they are willing to exhibit a reasonable degree of transparency on their program, and IF they can show that they had the weapons before the NPT and exactly how they were able to develop them in secret.
"The law is reason, free from passion."