50 USC Appendix § 2170.Kerad said:
Authority to review certain mergers, acquisitions, and takeovers
(a) Investigations
The President or the President's designee may make an investigation to determine the effects on national security of mergers, acquisitions, and takeovers proposed or pending on or after the date of enactment of this section [Aug. 23, 1988] by or with foreign persons which could result in foreign control of persons engaged in interstate commerce in the United States. If it is determined that an investigation should be undertaken, it shall commence no later than 30 days after receipt by the President or the President's designee of written notification of the proposed or pending merger, acquisition, or takeover as prescribed by regulations promulgated pursuant to this section. Such investigation shall be completed no later than 45 days after such determination.
(b) Mandatory investigations
The President or the President's designee shall make an investigation, as described in subsection (a), in any instance in which an entity controlled by or acting on behalf of a foreign government seeks to engage in any merger, acquisition, or takeover which could result in control of a person engaged in interstate commerce in the United States that could affect the national security of the United States.
It seems that the law is left open as to whether or not the investigation is mandatory based on if the deal could impact national security or not. As port security will remain under the Coast Guard, Customs, and Homeland Security it might just prove out to be that an investigation is not required for simply changing ownership of the company conducting the operations of the port between one foreign operator and another.
