Perhaps it is you who should read on.
UN Charter Chapter VII
Article 42 - Should the Security Council consider that measures provided for in Article 41 would be inadequate or have proved to be inadequate, it may take such action by air, sea, or land forces as may be necessary to maintain or restore international peace and security. Such action may include demonstrations, blockade, and other operations by air, sea, or land forces of Members of the United Nations.
Article 43 - 1) All Members of the United Nations, in order to contribute to the maintenance of international peace and security, undertake to make available to the Security Council, on its call and in accordance with a special agreement or agreements, armed forces, assistance, and facilities, including rights of passage, necessary for the purpose of maintaining international peace and security.
2) Such agreement or agreements shall govern the numbers and types of forces, their degree of readiness and general location, and the nature of the facilities and assistance to be provided.
3) The agreement or agreements shall be negotiated as soon as possible on the initiative of the Security Council. They shall be concluded between the Security Council and Members or between the Security Council and groups of Members and shall be subject to ratification by the signatory states in accordance with their respective constitutional processes.
http://www.un.org/aboutun/charter/chapter7.htm
Now, the UN Participation Act states that any agreements "shall be subject to the approval of the Congress by appropriate Act or joint resolution." Once the approval has been given by Congress, the President, as Commander in Chief, may then send the troops if he wishes. Congressional approval is needed for the special agreement, not for the subsequent implementation of that agreement.
http://www.law.berkeley.edu/faculty/yooj/courses/forrel/reserve/fisher.htm
Congressional approval was never given. New was absolutely right. Since Congress never gave approval to the agreement for US troops to be a part of this UN mission, the order was illegal.
Congressional approval wasn't needed. New was wrong, and by refusing to hear his case the Courts agreed that he was wrong.