Biden speaks on civil rights, Supreme Court proposals at LBJ Presidential Library

President Joe Biden on Monday visited the LBJ Presidential Library to mark the 60th anniversary of the Civil Rights Act and gave remarks on his new proposals to reform the U.S. Supreme Court.

The remarks were Biden's first major speech since his Oval Office address last week on his decision to exit the 2024 race.

In Austin, Texas, he discussed his administration's work to protect civil rights and his calls for reforms to the nation's highest court, including term limits and an enforceable code of conduct for justices as well as a constitutional amendment against presidential immunity.

"In recent years, extreme opinions that the Supreme Court has handed down have undermined long established civil rights principles and protections," Biden said.

"I have respect for institutions and the separation of powers laid out in the Constitution, but what's happening now is not consistent with that doctrine of separation of powers. Extremism is undermining the public confidence in the court's decisions," he continued, checking off recent decisions that he said led him to the reform proposals, saying those decisions have "undermined long established civil rights principles and protections."

"And most recently and most shockingly, the Supreme Court established in Trump vs. the United States a dangerous precedent," Biden said. "They ruled, as you know, that the president of the United States has immunity for potential crimes he may have committed while in office, immunity. This nation is founded on the principle that there are no kings in America. Each of us is equal before the law. No one is above the law!"

The setting for Monday's remarks was also significant, as Biden is the first sitting president since Lyndon B. Johnson to not seek reelection.

In stepping away from the campaign trail, Biden's focus is now shifted to how to "finish the job" in the final few months of his presidency and cement the legacy of his decades-long political career.

"The president is focused like a laser beam on making sure that the next six months matter to the American people," Stephen Benjamin, the director of the White House Office of Public Engagement, told reporters on Monday. "He is soliciting the ideas and thoughts of the best and brightest people in this administration, but also from across the country, asking people, 'What is left undone, what else do we need to work to secure?'"

Benjamin said he expects the president to continue to work on accountability for the Supreme Court, fortifying the economy, lowering prices for American families and more.

On his 18-year term limit proposal, Biden said this will help ensure that the court changes with some regularity and would remove "an extreme court attacking the confirmation process."

"That would make timing for the court's nomination more predictable and less arbitrary. And reduce the chance that any single presidency imposes undue influence on generations to come," he said.

Republicans in Congress signaled they are ready to challenge Biden's agenda.

House Speaker Mike Johnson slammed the proposed Supreme Court reforms, which Biden is floating after several court controversies this term, as "dangerous" and said they are "dead on arrival in the House."

Senate Minority Leader Mitch McConnell also argued in floor remarks that the administration is pushing for reform because they don't agree politically with the court's recent decisions.

"Why is the Biden Harris administration so willing to put the crown jewel of our system of government, the independent judiciary, to the torch? Because it stands in their way," McConnell said.

In closing, Biden spoke about Vice President Kamala Harris -- who has now taken the torch from Biden as the front-runner for the Democratic presidential nomination.

"I've made clear how I feel about Kamala," Biden said. "She has been a champion of rights throughout her career. She will continue to be an inspiring leader and project the very ideal of America."

ABC News' Lauren Peller and Allison Pecorin contributed to this report.