Without signing the NPT (explained below), Israel has not been legally eligible to receive aid from the US.
From: Zero Hedge
Leaked Colin Powell Email Confirms Israel Has “200 Nukes All Targeted On Tehran”
In the Leeds email dated March 3, 2015, Powell writes that “Iranians can’t use [a nuke] if they finally make one,” in the context of the ongoing talks about Tehran’s nuclear program. “The boys in Tehran know Israel has 200, all targeted on Tehran, and we have thousands. …
There is another reason why Powell’s email is troubling: a 1976 amendment to the Foreign Assistance Act bans any US economic and military aid to countries that deliver, receive, acquire or transfer nuclear enrichment technology without abiding by the NPT. Israel is one of the few countries that did not sign the NPT, along with self-admitted nuclear powers India and Pakistan.