For many Democrats, the aftermath of the Mueller report raised one central question: Would Robert S. Mueller III have charged President Trump with a crime if Justice Department policy had not prevented him from doing so?

On Friday, Senator Elizabeth Warren said the answer was yes.

Ms. Warren, who is seeking the Democratic nomination for president, proposed legislation she said was aimed at ensuring that “no President is above the law.” She called on Congress to pass a law clarifying that the Justice Department can in fact indict the president of the United States, while also renewing her call to begin impeachment proceedings against Mr. Trump.

“Mueller’s statement made clear what those of us who have read his report already knew: He’s referring Donald Trump for impeachment, and it’s up to Congress to act,” she wrote in a post on Medium.

“But impeachment isn’t supposed to be the only way that a President can be held accountable for committing a crime,” she wrote. “Congress should make it clear that Presidents can be indicted for criminal activity, including obstruction of justice. And when I’m President, I’ll appoint Justice Department officials who will reverse flawed policies so no President is shielded from criminal accountability.”