Donald Trump has immunity from criminal prosecution over some actions he took as president while fighting to subvert the 2020 election, the Supreme Court ruled Monday, further complicating efforts to put Trump on trial in Washington on criminal charges that he engaged in fraud to try to cling to power.

The decision, which divided the court along ideological lines, immediately knocked out some of the central allegations that special counsel Jack Smith leveled against Trump, including claims that he attempted to weaponize his Justice Department to concoct or amplify false claims of voter fraud.

However, the opinion also leaves much unresolved, sending the case back to the trial court for further proceedings. There, U.S. District Judge Tanya Chutkan must now sift through the allegations to separate Trump’s official acts — those he took in his capacity as president — from private ones, when he was acting as a presidential candidate. That process could further stall the case by months and is likely to push any trial past Election Day.

The opinion from Chief Justice John Roberts declared that former presidents have “absolute” immunity from criminal prosecution over actions that fall within their “core constitutional powers.”

“There is no immunity,” Roberts wrote, for “unofficial acts.”