Israel is party to the Convention on the Privileges and Immunities of the UN. The Convention makes UN premises inviolable – in other words, immune from search and/or seizure – and makes UN property and assets immune from legal process.
The International Court of Justice has also underscored that Israel is obliged to cooperate with UNRWA and other UN agencies.
There can be no exceptions. To allow this represents a new challenge to international law, one that creates a dangerous precedent anywhere else the UN is present across the world.