Every recent president has promised to reform South Korea’s notoriously powerful agencies, such as the spy agency, prosecution, tax office, antitrust watchdog and so on. President Moon Jae-in is no exception.

At the core of Moon’s promise is that his administration will depart from the past practice of the government in power using those agencies for political purposes.

Moon has already taken some actions, including radical reshuffles of senior officials, to overhaul the prosecution, which has borne the brunt of public criticism over the corruption scandal involving ousted President Park Geun-hye. Now Moon is set to target the spy agency.

The National Intelligence Service has a long history in the dark side of Korean politics. It was created by the late President Park Chung-hee under the name Korean Central Intelligence Agency. It played a key role in extenuating the former Army general’s authoritarian rule.

Park’s successor, Chun Doo-hwan, another military strongman, made only cosmetic changes like renaming it the Agency for National Security Planning. It continued to serve as the main tool for his harsh dictatorial rule.

Kim Dae-jung, a dissident who had suffered a lot at the hands of the agency, again changed its name to the current National Intelligence Service, but even he failed to completely sever its subordination to the government in power. NIS agents kept interfering with domestic politics and stood at the forefront of his “Sunshine Policy” of engaging North Korea.

During his election campaign, Moon pledged that he would make sure the NIS takes its hands off domestic intelligence. He even indicated giving the agency a new name -- like the overseas and security intelligence service -- to back his commitment.

Moon’s argument is understandable to some extent, given the spy agency’s ceaseless intervention in domestic politics and abuse of power.

In some sense, Moon himself was a victim of the agency’s intervention in politics: NIS agents engaged in cyber activities in support of his rival candidate Park Geun-hye during the 2012 presidential election. Moon did not lose the election only because of the NIS activities, but the case demonstrates how difficult it is to end the agency’s vicious tradition of serving the political interests of the government.

Nevertheless, there have been growing concerns over Moon’s avowal to ban the NIS from all domestic intelligence operations. Even Moon’s nominee to head the NIS seemed skeptical of the plan.

In his parliamentary confirmation hearing Monday, Suh Hoon said that he would make sure the NIS is completely cut off from domestic politics. But he quickly added that it would be impractical to prohibit the NIS from all domestic intelligence activities.

As Suh noted, it is difficult to make a clear distinction between all domestic and overseas intelligence, especially at a time when nations face growing threats of terrorism, including those against soft targets, cross-border drug crimes, industrial espionage and cyberattacks. Moreover, we live with constant security threats from North Korea.

It is fortunate that the nominee has more realistic thinking than his boss on how to approach the issue. Key in the reform plan -- as Suh said in the hearing -- should be how to bar the NIS from activities like gathering information on domestic politics, interfering with elections and putting civilians under illegal surveillance. A blanket ban on domestic intelligence operations will only weaken national security.

The main reason the NIS -- or whatever name it had in the past -- has failed to end its bad practices was not the lack of a law banning it from all domestic intelligence operations or a name suggesting it only deal with overseas and security-related intelligence.

The real reason was that all the past presidents failed to resist the temptation to use the agency as a political tool and the agency was all too submissive to the government in power. This is what Moon has to overcome to allow the NIS to be reborn as a trusted institution.