Peter Zeidenberg is a partner at Arent Fox's White Collar & Investigations Practice, where he defends scientists and other individuals and companies in white collar criminal matters. He spent 17 years as a federal prosecutor at the Justice Department, where he was a deputy special counsel in the investigation and prosecution of I. Lewis "Scooter" Libby. The opinions expressed in this commentary are his own.

(CNN) Deputy Attorney General Rod Rosenstein's pronouncement Tuesday that the Justice Department must do "what's required by the rule of law" and must remain insulated from politics should not have been necessary. There was a time, not very long ago, when the necessity of a Justice Department free from political influence was not a controversial position. Unfortunately, things have changed and, today, law enforcement is under attack.

Americans have heard the President dismiss the work of career public servants as "an attack on our country in a true sense." The Department of Justice and the Federal Bureau of Investigation have been tarred as "embarrassment[s] to our country."

These are just a couple of the comments that have justifiably raised suspicion that the President may soon attempt to remove Robert Mueller from his role as special counsel overseeing the Russia investigation, speculation only further fueled by Wednesday's reporting suggesting Mueller could soon subpoena the President. Firing Mueller would be a grave mistake, and Americans of all political stripes must stand together to do everything possible to prevent it from happening. The stakes are real, and the potential consequences would be far-reaching.

If we want to ensure the sanctity of our democracy, the Mueller investigation must proceed without impediment. The allegations being investigated -- a possible connection between the Russian government and Trump's 2016 presidential campaign -- could not be more serious. And, just as importantly, if allegations of wrongdoing cannot be substantiated, an enormous cloud of suspicion will be lifted off the President and his administration. Whatever the outcome, answers must be uncovered.

Mueller's law enforcement career earned him the well-deserved respect and admiration of both political parties. In 2001, President George W. Bush nominated Mueller to a 10-year term as FBI director; he was confirmed by the Senate in a 98-0 vote. In 2011, President Barack Obama nominated Mueller for an unprecedented, additional two-year term, and the Senate again acted unanimously to approve this extension. Virtually all who know him --including myself -- can attest that he is a man of unimpeachable character. It should come as no surprise, then, that many view the attacks on Mueller's integrity by the President and his allies as offensive.

Still more troubling, though, is the danger these threats pose to our democracy. Mueller must be able to exercise his authority, overseen by an independent judiciary, to investigate and prosecute any wrongdoing that he uncovers. The attack on Mueller does not just make his job harder to do, it undermines respect for the law and threatens America's justice system.

In moments such as these, when law enforcement is under attack, we have one important recourse: our elected officials who make the laws. Yet too many lawmakers have turned a blind eye or echoed the President's sentiments. This is unconscionable and it must end.

It is heartening that in the Senate Judiciary Committee, we saw a bipartisan breakthrough when Sens. Lindsey Graham, R-South Carolina; Thom Tillis, R-North Carolina; Chris Coons, D-Delaware; and Cory Booker, D-New Jersey, shepherded through a compromise bill to protect the special counsel. But it never should have come to this, and it certainly should not be doomed now by Majority Leader Mitch McConnell's promise never to bring the legislation to a vote in the Senate. Congress must speak out for the independence of our justice system -- and the importance of protecting the special counsel's investigation from interference or undue influence. What's at stake is the basic proposition that defines the American experiment: the notion that our government, as John Adams wrote, is one "of laws, and not of men."

Join us on Twitter and Facebook

Our justice system relies on the faith of ordinary Americans. This bedrock is imperiled by attempts to impugn the integrity of those who are committed to protecting our democracy -- officials like Robert Mueller. At this critical juncture, we must protect the independence of our justice system and permit it to do its job. It is time for Congress to act, and to ensure the justice system be permitted to work.

Successive generations of Americans have argued, fought and sacrificed to defend a system predicated on the rule of law. We all must defend it again today.