Now that a federal judge has ruled that White House aides, even legal counsel, must comply with congressional subpoenas, President Trump should look back to his favorite predecessor for guidance on how to proceed.

The Republican-led House investigation into the alleged targeting of conservative groups by the IRS climaxed in May 2013 when Lois Lerner, who had been an agency official, was subpoenaed by Congress to testify. She showed up, gave a brief statement about having committed no wrongdoing, and then pleaded the Fifth.

She took no questions and left Republicans mad over the waste of time.

The House voted thereafter to hold Lerner in contempt of Congress, but the U.S. attorney's office of Washington, D.C., declined to prosecute her, maintaining that she had an absolute right to take the Fifth and that, contrary to what Republicans believed, she did not waive that right simply by offering an opening statement on her innocence.

This week, the judge's ruling only stated that White House aides are required to appear before Congress when handed a subpoena. But District Judge Ketanji Brown Jackson acknowledged that her decision didn't relate to any potential testimony that should or shouldn't be offered:

"But in this Court’s view, the withholding of such information from the public square in the national interest and at the behest of the President is a duty that the aide herself possesses. Furthermore, as previously mentioned, in the context of compelled congressional testimony, such withholding is properly and lawfully executed on a question-by-question basis through the invocation of a privilege, where appropriate. As such, with the exception of the recognized restrictions on the ability of current and former public officials to disclose certain protected information, such officials (including senior-level presidential aides) still enjoy the full measure of freedom that the Constitution affords."

In other words, White House officials have to show up. But when they do, they don't necessarily have to say anything at all.

The White House's position before the ruling has been that all staff, current and prior, are covered by executive privilege and thus could defy subpoenas by order of the president. Brown Jackson says they can't ignore the mandate to physically appear, but suggests it's an open question as to whether their testimonies are covered under executive privilege. That issue will likely have to be settled by yet more legal decisions.

Even if House Democrats have already indicated that they're ready to impeach with zeal as soon as next week, their numerous, endless investigations of the president will continue into 2020 and, if Trump wins reelection, beyond.

He doesn't have to worry about subpoenas anymore. Just tell White House staff to pull a Lois Lerner.