Israeli legislation taking effect on Thursday will threaten the operations of a major United Nations agency that provides critical humanitarian aid in the Gaza Strip after more than a year of war has left the territory in ruins.

The laws ban the agency, UNRWA, from any activities in Israel, effectively cutting off its ability to deliver aid to Gaza. The agency, known formally as the United Nations Relief and Works Agency for Palestine Refugees in the Near East, provides shelter, food and water to millions of Palestinians not only in the enclave, but also in the Israeli-occupied West Bank and several surrounding countries.

Israel accuses UNRWA of acting under Hamas’s influence, rendering it incapable of behaving as a neutral aid group. Israel says UNRWA employs many Hamas members, including some who joined the Hamas-led attacks on Israel.

Israel has argued that other U.N. agencies and aid groups can step up in UNRWA’s place. But aid officials say that removing the U.N. agency, the largest humanitarian organization in Gaza, will severely undermine aid efforts.

COGAT, the Israeli military unit responsible for coordinating aid deliveries to Gaza, has said that it is subordinate to Israeli law and that the government and will “implement the law as best as possible.”

Here is a look at what the ban could mean for Palestinians in Gaza and beyond.