If necessary, members of Congress could unilaterally release classified information on the floor of the House or the Senate. The Constitution’s speech and debate clause would protect them from criminal prosecution and civil lawsuits. If Mr. Trump attempted any legal action, courts would almost certainly dismiss it on separation-of-powers grounds. With bipartisan support, Congress could even pass a new statute specifically to declassify key documents, overriding a presidential veto if necessary.

If individual whistle-blowers know what to ask for, they can also litigate. To force the government to release specific classified documents, they can follow administrative declassification procedures and sue under the Freedom of Information Act. Any Justice Department official who destroyed documents during litigation would be violating multiple criminal statutes. In such a high-profile case, it’s hard to say how successful such litigation would be, but in other matters, journalists have quite often won such lawsuits against the government.

Mr. Mueller could also write an article describing what he learned, and submit it to the Department of Justice for prepublication review for classified material. If the department insists on redacting even one word, Mr. Mueller could sue to enforce his own First Amendment rights to communicate with the American people on matters of public concern. Courts have sometimes ruled favorably in less-prominent cases.

President Trump and the Justice Department could certainly try to make these whistle-blowers’ lives difficult. They could drag the cases out for lengthy periods of time or even seek to prosecute the whistle-blowers based on various legal theories.

These mechanisms are imperfect and would produce uncertain results. And they’re still risky. A whistle-blower giving a media interview could inadvertently disclose classified information and wind up in prison. But these mechanisms are lawful.

As you read these words, it is likely that a handful of civil servants are out there, sitting on evidence of official lawbreaking that none of us know about. We don’t yet know their names. But if we enter a constitutional crisis, they could play a special role in defending the republic. They are national heroes waiting to be born.