Executive privilege can shield President Trump's communications with "private advisers" outside of the government, the Justice Department's Office of Legal Counsel concluded Monday.Why it matters: Democrats have been planning to bypass expected White House stonewalling by subpoenaing companies, colleges and private citizens if they win enough seats in November. The new opinion could create a new hurdle for Democrats should they retake Congress."It really could be a pretty significant weapon" for the administration "to deflect a lot of that congressional investigation of private parties," says Jonathan Shaub, a University of Kentucky law professor and former OLC attorney.The fine print: "The need for presidential confidentiality applies to communications with private advisers just as it does with government officials," the opinion reads, arguing outside sources may be less willing to give advice if they fear public disclosure.The OLC said privilege applies when three boxes are checked: The communications must "relate to official presidential decisionmaking," "involve or reflect communications" with the president or his direct advisers, and remain confidential.The memo's release was first reported by Punchbowl News.Beyond its implications for future fights on the Hill, the opinion comes as Boris Epshteyn, Trump's senior personal counsel, fights a subpoena from the American Bar Association over deals the administration struck with law firms.Reality check: Even if the memo offers a legal argument for individuals fighting subpoenas, Shaub doubts courts will buy into the OLC's theory.Shaub tells Axios that while the OLC has long held a broad interpretation of executive privilege, this goes beyond anything it's formally ruled in the past."The understanding was the general public and the courts would never accept this," he says. However, "this OLC doesn't seem hesitant to make these broad, sweeping claims."And while it could be a roadblock for lawmakers seeking information from private parties, it only applies to presidential duties, Shaub says. A probe into something like Trump's cryptocurrency empire may be harder to defend as privileged.What they're saying: A DOJ official told Axios in a statement that the "issue has not been litigated frequently," but the opinion "reaffirms the longstanding position of the office going back at least as far as Paul Clement in 2007 and arguably as far back as 1972."Catch up quick: The Trump administration has intermingled with the private sector in historic ways and has built a political orbit that stretches far beyond his Cabinet into business, tech, media and his family.The Trump administration has taken other steps to shield records from the public, including declaring the post-Watergate Presidential Records Act of 1978 unconstitutional (in a memo that was later shot down by a federal judge).What we're watching: The OLC opinion lands as the administration's legal apparatus undergoes a makeover: Todd Blanche was formally sworn in as attorney general, and White House staff secretary Will Scharf will soon take over as White House counsel.If the midterms go well for Democrats, that could put Scharf at the center of debates over executive privilege.Go deeper: Inside Trump's assault on public records