Prime Minister Benjamin Netanyahu's rightist coalition weathered a lengthy parliamentary debate on Thursday, with 46 politicians in favour and 40 opposed in the 120-seat Knesset.
Head of the Palestinian Prisoners Commission, said that the law legalises murder.
"It's against Geneva Conventions and international humanitarian law, it legalises torture of prisoners who are demanding their rights in a non-violent way," he said.
Qaraqe asked for a meeting of state parties to the Geneva Conventions to take a stand against the law and demand Israel not apply it.
Israel says it is concerned that hunger strikes by Palestinians in its jails could end in death and trigger waves of protests in the occupied West Bank and East Jerusalem.
Israel's Medical Association, which considers force-feeding a form of torture, has urged Israeli doctors not to abide by the law