The Paris Declaration Respecting Maritime Law, cited in a United Nations report on the raid which concluded that the blockade had been a legitimate and legally implemented response to an act of aggression, states that "The neutral flag covers enemy's goods, with the exception of contraband of war".
As Israel is not a party to the Vienna Convention on the Law of Treaties, there are no international agreements restricting the ability for Palestine to unilaterally exit from the Gaza-Jericho Agreement.