Prosecuting Donald Trump is going to be much more difficult after the Supreme Court's decision on presidential immunity, legal experts said.

The Supreme Court ruled that Trump has absolute immunity for core presidential acts and "presumptive immunity" for acts within the outer perimeter of official presidential acts. In addition, it ruled that a president has "evidentiary immunity," so prosecutors can't use evidence gathered from Trump's official acts to build a case for alleged crimes committed outside of his presidential role.

"The court's decision delivers a real mess for the trial court to sort out, while preserving the court's ability to second guess whatever they do," Greg Germain, a law professor at Syracuse University in New York, told Newsweek.

The case arose after Trump was indicted on four counts of allegedly working to overturn the results of the 2020 election in the run-up to the January 6, 2021, riot at the U.S. Capitol. Trump was facing the charges as the frontrunner for the Republican presidential nomination. He has pleaded not guilty and repeatedly said he is the victim of a political witch hunt.

The case was frozen while the Supreme Court considered the presidential immunity issue.

Newsweek sought email comment on Tuesday from Donald Trump's attorney.

Germain said the decision has helped Trump as charges relating to his communications with the attorney general and with Mike Pence, the then vice president, will likely have to be dropped.

"I think it's a very messy opinion which provides little guidance to the lower court on how to proceed, except to recognize that the claims regarding communications with the attorney general must be dismissed, and the claims relating to communications with Pence will likely have to be dismissed," he said.

Germain added that it is now "very hard to see this case coming to trial before the election.

"There was a lot of speculation that the Republican-appointed majority of the Court took the immunity case because it wanted to delay the trial until after the election. But the decision shows that the majority clearly disagreed with the lower courts' rulings, and wanted to make sure that the court's much broader views of presidential immunity would be applied before subjecting Trump to a trial.

"The district court had held that Trump had no immunity for official or unofficial acts. The D.C. circuit held that Trump had immunity for mandatory official acts, but not for discretionary official acts.

"The Supreme Court broadly rejected the approach used by the lower courts: President Trump has absolute immunity (even evidentiary immunity) for a president's 'core constitutional powers', has 'presumptive immunity' for acts within the outer perimeter of official presidential acts, and has no immunity for private or unofficial acts."

New York University law professor Peter Shane told Newsweek that "the biggest loss for the government" is that the court has ruled out "prosecuting Trump for anything he did in connection with the U.S. Justice Department because of his supervisory authority over the department. Even worse, his interactions with the Department of Justice can't be used as evidence in prosecuting Trump for anything else," he said.

President Joe Biden said after Monday's ruling that it was "highly, highly unlikely" that Trump would face trial before the 2024 election.

He strongly condemned the decision and said it would embolden Trump to do whatever he wanted.