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Long answer
Israel and Egypt have a right to choose who and what crosses their borders, especially when dealing with Hamas controlled Gaza. Remember that Hamas is a terrorist organization similar to ISIS, with a stated purpose of annihilating Israel and establishing a Jihadist Muslim Caliphate throughout the Middle East, and a long history of smuggling weapons to use in its attacks against Israel. No country in the world is required to allow uninterrupted crossing of its borders without any restrictions, so why should Israel or Egypt be treated differently? This also does not mean that goods or humanitarian aid are not allowed to enter Gaza – but it does mean that those goods need to be checked for weapons or materials that can be turned into weapons.