This compact shall be open to joinder by any state, territory or possession of the United States, the District of Columbia, the Commonwealth of Puerto Rico, and with the consent of Congress, the government of Canada or any province thereof. It shall become effective with respect to any such jurisdiction when such jurisdiction has enacted the same into law. Withdrawal from this compact shall be by the enactment of a statute repealing the same, but shall not take effect until two years after the effective date of such statute and until written notice of the withdrawal has been given by the withdrawing state to the governor of each other party jurisdiction. Withdrawal of a party state shall not affect the rights, duties and obligations under this compact of any sending agency therein with respect to a placement made prior to the effective date of withdrawal.