(CNN) A few years after President Richard Nixon resigned, Attorney General Griffin Bell gathered Justice Department lawyers in the department's elaborate Great Hall to address their independence in the post-Watergate world.

"The partisan activities of some attorneys general ... combined with the unfortunate legacy of Watergate, have given rise to the understandable public concern that some decisions at Justice may be the products of favor, or pressure, or politics," he said in the September 6, 1978 address

Resulting Justice Department rules limited White House involvement with law enforcement decisions. The reforms emerged from Nixon's use of the department to conceal his administration's involvement in the break-in at the Democratic National Committee in the Watergate building.

Those decades-old reforms were invoked again on Friday, after news that President Donald Trump personally intervened to try to lift a gag order on an undercover FBI informant sought by Republican members of Congress in an investigation of Russian nuclear industry efforts to gain influence in the United States during the Obama administration.

It was only the latest chapter in ongoing controversy over White House intervention at DOJ since Trump took office. He has routinely injected himself in politically charged law enforcement matters, including those related to the probe of the Russian government's influence in the 2016 presidential election and potential ties to his campaign.

Speaking on CNN's "New Day" Friday, Sen. Richard Blumenthal, D-Connecticut, deemed the recent disclosure part of a pattern of intervention and "politicization," which included the May firing of FBI Director James Comey, who was overseeing the investigation into Russia's election interference.

"There were rules in the wake of ... the Nixon improprieties that presidents would not interfere or intervene in ongoing investigations," Blumenthal said. "Those norms seem to be violated."

Former Sen. Rick Santorum, a Pennsylvania Republican, countered on CNN's "Newsroom," "Donald Trump has every right as President of the United States to advise the Justice Department as to his opinion on these things. I don't have a problem with this at all. It's about providing more information, not less. And I think that's a good thing."

Separately on Friday, White House adviser Kellyanne Conway told "New Day," "He believes, as many others do, frankly, that the FBI informant should be free to say what he knows."

CNN reported Thursday that Trump told his staff to work with the Justice Department to allow a former undercover FBI informant to testify. Republicans on Capitol Hill are investigating the circumstances surrounding the sale of a uranium mining company to Russia's Atomic Energy Agency, Rosatom. The deal was approved by the Committee on Foreign Investment in the United States, a panel composed of representatives from several US government agencies, including the State Department, which at the time was led by Hillary Clinton.

A source familiar with the matter told CNN that the DOJ move to allow the informant to speak to members of Congress was made independent of any communications from Trump.

Trump's constant interactions with the Justice Department, FBI and US attorneys -- against the backdrop of special prosecutor Robert Mueller's Russia investigation -- cannot help but recall the Watergate era. Nixon Attorney General John Mitchell was convicted and served time in prison for his role in the scandal.

Bell, in his 1978 speech, said he worked for almost two years to develop rules to make DOJ "a neutral zone," with the foundation being that the White House should steer clear of law enforcement decisions and the daily operations of the career staff involved in investigations and prosecutions.

Bell, who served in the Jimmy Carter administration and died in 2009, noted that under the Constitution, the attorney general is responsible to the president and the president to the public. So, he said, "true institutional independence is therefore impossible." But he emphasized, "the president is best served if the attorney general and the lawyers who assist him are free to exercise their professional judgments."

To be sure, not all interactions between the attorney general and president since then have been true to that principle. But at least it has been the ideal. "What must be avoided, in fact and in appearance," Bell said, "is pressure from any source that is intended to influence our legal judgment."

As he began his address nearly four decades ago, Bell told the audience he was using a prepared text, "because it's an important subject, something that I hope will be left here for years to come."