President Trump raged on Twitter last week about Attorney General Jeff Sessions’ decision to have the Justice Department’s Inspector General investigate the FBI’s possible misuse of the Foreign Intelligence Surveillance Act.

“Why is A.G. Jeff Sessions asking the Inspector General to investigate potentially massive FISA abuse,” Trump tweeted. “Will take forever, has no prosecutorial power and already late with reports on Comey etc. Isn’t the I.G. an Obama guy? Why not use Justice Department lawyers? DISGRACEFUL!”

The president may be surprised to learn that the Justice Department’s inspector general, Michael Horowitz, testified to the Senate Judiciary Committee in August 2015 that the Obama administration was stonewalling his investigations.

The position of inspector general, independent investigators who work inside government agencies, was created by a 1978 law in the wake of the Watergate scandal, still one of history’s most visible examples of the abuse of executive power, though not the most recent one.

In August 2014, 47 of the government’s inspectors general signed a letter to Congress complaining that several agencies, including the Justice Department, were withholding information on the questionable basis that it was “privileged.”

At the Senate Judiciary Committee hearing, Inspector General Horowitz described the Obama administration policy shift that limited cooperation with IG investigations.

“The problem of our access to information is a relatively new one,” Horowitz said. “Prior to 2010, neither the Justice Department nor the FBI questioned our legal authority to access all documents in its possession, and we obtained grand jury wiretap and credit information without legal objection and without the need for a legal opinion. Indeed, it would be hard to imagine how we could conduct effective oversight of the FBI, the DEA, and other law enforcement components if we were prohibited from reviewing information like grand jury and wiretap information that those agencies frequently use.”

Horowitz explained that the IGs handle sensitive information with great care and in compliance with all laws limiting the use and disclosure of the information.

“There has not been a single occasion in our 27-year history where we have been accused of mishandling such information,” he testified. “However, in 2010, FBI lawyers concluded that our office could not have legal access to such information, despite its past practice and despite the fact that no laws had changed. FBI lawyers also identified 10 other categories of records where they believed we might not be entitled to access. Since that time, our office has faced numerous challenges to our access to department records, seriously impacting our ability to conduct oversight.”

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Hold off on Ruth Bader Ginsburg replacement: Tom Campbell Then in 2014, Horowitz said, the Obama administration’s Office of Legal Counsel issued an opinion stating that the Inspector General Act of 1978 does not entitle the IG to access grand jury, wiretap or credit information.

“The legal underpinning of the OLC opinion represents a serious threat to not only my independence, but to that of all inspectors general” Horowitz told the lawmakers. “For the first time since the I.G. Act was passed in 1978, the word ‘all’ in Section 6(a) of the I.G. Act no longer means all.”

For the last year, Inspector General Horowitz has been investigating possible “improper considerations” in the FBI and Justice Department’s handling of the Clinton email investigation, and now he’ll look into the possible abuse of FISA to spy on the Trump campaign.

President Trump should check on the status of that 2014 Office of Legal Counsel opinion. If it’s still in force, he has a pen and a phone.

Susan Shelley is an editorial writer and columnist for the Southern California News Group. Reach her at Susan@SusanShelley.com and follow her on Twitter: @Susan_Shelley.