What vulnerabilities are presented between the Maritime Transportation Security Act (MTSA) and the Safe Port Act combined? Do they complement each other or are they counterproductive?

The Maritime Transportation Safety Act of 2002, which represented the effort on the part of the United States to comply with the International Ship and Port Facility Code, which was negotiated during the same period of time, was primarily a response to the terrorist attacks of September 11, 2001.
The attacks by terrorists affiliated with al Qaeda on the World Trade Center in New York City, the Pentagon in Arlington, Virginia, and the third, unidentified target in Washington, D.C. (most likely the U.S. Capitol building) shocked most Americans and their elected representatives. While the vulnerability of many potential targets of attack across the United States had been recognized for many years prior to the 9-11 attacks, however, little had been done to address those vulnerabilities. Potential terrorist targets like railways, nuclear power plants, subways, electrical power grids and others were assessed by multiple government and private organizations. Among the vulnerabilities identified in the aftermath of the 9-11 attacks were the ports and related facilities that regularly facilitate the transit of thousands of shipping containers every day. The potential of hostile governments and/or nongovernmental organizations like al Qaeda to deliver into the United States so-called Weapons of Mass Destruction (nuclear bombs, including “dirty bombs” that use conventional explosives to spread deadly radioactive materials, chemical and biological weapons) through shipping containers was and remains one of the United States’ most glaring vulnerabilities.
It was in the context of these heightened concerns regarding the country’s vulnerability to terrorist attacks through large ports through which transit those thousands of large shipping containers on a daily basis that the United States and its allies and trade partners abroad negotiated conditions intended to lessen that vulnerability. The problem, after all, does not only involve American ports that receive shipping containers; American security experts recognized that there existed a requirement on the other end—at the foreign ports where those containers originated or through which they transited—for greatly increased monitoring of the contents of containers bound for the United States. The early result was the Maritime Transportation Security Act. The Act’s many provisions included requirements for all relevant parties to improve the systems by which they screen and train employees and monitor shipping for banned or dangerous cargoes.
Vulnerabilities to terrorist actions were not the only threat to which the Act was oriented. The age-old problem of narcotics smuggling was a natural and obligatory issue that was addressed in the legislation (which passed into law as Public Law 107-295). Terrorism, however, was the higher priority, and ports around the world were now required to develop or purchase and use whatever advanced technologies existed to facilitate the enormously difficult task of screening shipping containers. Because of the huge number of containers entering and leaving major ports in such cities as Los Angeles, Baltimore, Dubai, Singapore, Tokyo, Kobe and others, it is not possible to visually inspect every container. The means had to be developed, therefore, to scan the interior contents of closed containers through x-ray-type imaging and sensors to detect fissionable materials (those materials like processed uranium and plutonium used in the manufacture of nuclear weapons). All of this was the intent and constitutes the content of the Maritime Transportation Security Act.
Because initial reactions to crises like the Maritime Transportation Security Act inevitably prove insufficient or impractical, subsequent measures are almost always required. This was the case with the Security and Accountability for Every (SAFE) Port Act of 2006 (Public Law 109-347). While there is considerable duplication in intent between the two Acts, and while both mandate improvements in the operations of port facilities both at home and abroad, the SAFE Port Act goes more extensively into certain areas, especially into the area of international communications between cooperating port facilities. Title VI of this act, for instance, includes requirements for emergency and short-notice communications between facilities and ships and between facilities in shipping and receiving partnership countries. Most significantly, the SAFE Port Act includes in Section II a subsection, “B,” titled “Customs-Trade Partnership Against Terrorism” (C-TPAT). This section authorizes the federal government to establish an enhanced partnership among allies and trade partners designed to minimize gaps or weaknesses in the supply chain integral to the operations of international shippers. The idea is to ensure that all elements of the supply chain, including carriers, customs brokers, forwarders and others are all operating off the same sheet of paper with regarding personnel management (screening and training of potential employees), use of available technologies to scan cargo, procedures for documentation, and so on.
In conclusion, there is overlap between the two Acts. That is to be expected given the propensity of review boards and congressional committees to revisit issues over time. Just as expected, however, are the additions to the earlier legislation represented in the later Act intended to address the earlier efforts shortcomings and to compensate for technological developments in the intervening period and the emergence of new or different proposals to address the underlying problem.
http://www.imo.org/en/ourwork/security/guide_to_maritime_security/pages/solas-xi-2%20isps%20code.aspx

https://www.congress.gov/109/plaws/publ347/PLAW-109publ347.pdf

https://www.govinfo.gov/content/pkg/PLAW-107publ295/html/PLAW-107publ295.htm