The appointment of another special counsel — this one over President Biden’s handling of classified documents — suggests that even Attorney General Garland saw the preposterousness of going after President Trump for mishandling documents without going after Mr. Biden. If no one is above the law, as the attorney general likes to boast, it strikes us that, with two investigations now under way, setting a single standard is at a premium.

We understand that differences may be marked between Messrs. Biden and Trump. Mr. Biden’s lawyers are said to have brought the discovery of classified documents on his premises to the attention of the authorities. Mr. Trump, in contrast, is said to have been dragging his feet on the production of documents throughout a long investigation. We wouldn’t discount it but wouldn’t want to make too much of it.

Then again, too, some distinctions work in Mr. Trump’s favor. He was, after all, president when the documents for which he’s being investigated were moved to Mar-a-Lago, and as president he has full authority to determine whether the documents were classified. Mr. Biden’s documents were disclosed not by any independent source, but by Mr. Biden’s own lawyers. The press has been remarkably credulous as to these lawyers’ accounts.

The press also appears to be taking at face value Mr. Biden’s claim to be “surprised” about the presence of the classified documents at his think tank and in his “locked” garage. That reaction, legal sage Jonathan Turley observes, echoes how “surprised” Secretary Clinton was when documents sought in the Whitewater investigation — described by the New York Times as “elusive” — appeared years later, after the investigation was over.

“Biden is taking a page from the Hillary Clinton playbook,” Mr. Turley suggests. If so, we can understand why. Mrs. Clinton and her lawyers were able to evade consequences over her use of a private email server for communications while she ran America’s foreign policy. That raised not only accusations of mishandling classified information but also questions over “missing” emails. Yet the State Department cleared her of any wrongdoing.

The questions at play over Mrs. Clinton’s emails — including the connections between donations to the Clinton Foundation and influence-seeking by foreign governments and others — are on a par with concerns raised about the president’s son, Hunter Biden, and his tangled web of business dealings with foreign enterprises, including a Ukrainian energy concern. When supporters of Mr. Trump plead “Drain the Swamp,” this is partly what they mean. 

So it’s not just Mr. Biden who complicates Mr. Garland’s work but also Mrs. Clinton and her notorious emails. The Democrats’ reticence and self-righteous hesitation to launch investigations into possible malfeasance by one of their own — like, say, Secretary Clinton, Hunter Biden, or President Biden — contrasts with their zeal to investigate Mr. Trump. All the more reason now to hold the Justice Department to a single standard.