Over 180 former senior officials — some of whom were appointed by Netanyahu — from Mossad, Shin Bet, military and police have united against steps they say will shatter Israel's resilience.
The hearing on Tuesday puts the country's senior justices in the unprecedented position of deciding whether to accept limits to their own powers.
Despite the fraught atmosphere, Netanyahu's allies say they are moving forward on the overhaul. Here's a look at how the overhaul could affect Israel in the coming months.
A country once known for left-leaning politics now has a right-wing government dominated by Jewish religious nationalists who spearheaded the efforts to curb judicial checks on executive power.
"A black day for Israeli democracy," read the blackened front pages of three of the country's top newspapers on Tuesday, carrying an advert by opponents of the judicial reforms.
"The doctors tell me that I will be free and I will be released from the hospital tomorrow afternoon and will be able to go to the Knesset to vote," Israeli Prime Minister Benjamin Netanyahu said.