President Donald Trump’s impeachment trial, like many of his administration’s actions before it, has ventured into uncharted legal territory.

The trial lacks definitive answers on key issues, either from federal courts or the Senate itself, which has fed an undercurrent of uncertainty about what happens next in an institution usually steeped in precedents and traditions.

How the Senate tackles these issues over the coming days — from the bar for removing a president to how witnesses testify at an impeachment trial — likely will set standards for presidential behavior and congressional oversight efforts long after Trump leaves office. Adding to the uncertainty were reports late Tuesday that there were now enough votes to call witnesses, but how many and the manner in which they would be examined or deposed was unknown.

Outside the Senate, federal courts have grappled for years with similar separation-of-powers issues prompted by the actions of Trump’s presidency.

There’s ongoing litigation over lawmakers seeking to enforce constitutional provisions about presidents benefiting financially from the office.

There’s also litigation on the ability of congressional investigators to subpoena a president’s tax returns and financial records, which is currently before the Supreme Court, and Trump’s emergency actions to spend unappropriated money on a border wall, as well as whether some former officials have “absolute immunity” from congressional subpoenas, and more.

Courts have yet to give a definitive answer on those issues.

Pressure on Senate

Now the Senate will confront unsettled questions of its own, such as whether articles of impeachment must allege a crime or the process for calling witnesses such as former national security adviser John Bolton.

The lingering uncertainty fuels the political pressure on the Senate and sparks debate among legal professors and Senate rules experts. And it underscores just how unpredictable the next few days and weeks could become.

“There are all sorts of holes in the law, but impeachments are incredibly rare, so there are, not surprisingly, still a lot of open issues in this context,” said Ross Garber, who teaches political investigations and impeachment at Tulane Law School.

The unanswered questions go to the heart of the impeachment charges, as well as what will happen in the rest of the trial itself.

A main part of Trump’s comparatively brief defense, presented to the Senate late Monday by former Harvard Law professor Alan Dershowitz, contends that the Senate should not convict because the articles of impeachment do not include a criminal violation.

Other constitutional law scholars widely disagree, as do Democratic senators.

“I willingly acknowledge that the academic consensus is that criminal conduct is not required for impeachment and that abuse of power and obstruction of Congress are sufficient,” Dershowitz told senators. “I do my own research, and I do my own thinking, and I have never bowed to the majority on intellectual or scholarly matters.”

The Senate’s decision, if made on the power of Dershowitz’s arguments, could establish a precedent of impeachment requiring a criminal allegation.

Some Democrats said Dershowitz mischaracterized the intentions of the framers of the Constitution, but some Republicans said they found it persuasive.

“Dershowitz eviscerates the Dems’ case tonight,” Missouri Republican Sen. Josh Hawley tweeted. “They have not charged an impeachable offense or alleged impeachable conduct. Period. Let’s vote”

More questions

Some House Democrats and some legal experts point out that although the two articles of impeachment are not crimes, they include the elements of bribery.

They say Trump used his official power to withhold military aid to Ukraine to obtain a “thing of value” to his campaign — a statement from the country’s president of an investigation into former Vice President Joe Biden and his son Hunter Biden.

But off the Hill, such a question has never been fully tested in a criminal court. And a “thing of value” is not well-defined, leaving sharp disagreement among legal experts about whether Congress could ban a candidate from asking a foreign government for help without stepping on the First Amendment.

Most of the unanswered questions now swirl around the possible testimony from Bolton, whose leaked book manuscript contains a passage that appears to undercut Trump’s defense in the impeachment trial that he did “absolutely nothing wrong.”

Among them: The process for compelling Bolton to testify, whether Trump could go to court to claim Bolton is immune from subpoenas, whether courts would enforce a subpoena in the impeachment context, whether Trump could claim executive privilege to block Bolton’s testimony, whether a Senate vote could override that executive privilege, and whether the courts would resolve that executive privilege dispute or leave it up to the Senate.

House managers say there is overwhelming evidence that Trump conditioned military aid to Ukraine on that country’s president announcing investigations into the Bidens.

Experts divided

The confusion about it is on and off Capitol Hill.

On Monday, two Georgetown University Law Center professors and a former member of Congress wrote an op-ed in The New York Times that said Senate impeachment rules stipulate that Chief Justice John G. Roberts Jr. is the decision-maker on subpoenas for key witnesses and has the power to issue them by himself.

The trio argued House managers should request Roberts issue subpoenas for witnesses. But Senate experts pointed out that their analysis overlooked a rule that says the Senate “has the power to compel the attendance of witnesses.”

“Senators can of course *try* the tactic proposed in the op-ed,” tweeted Sarah Binder, a political science professor at George Washington University. “But ultimately, the power of Democrats to succeed in calling witnesses is *likely* to depend on securing GOP votes for their procedural gambit.”

The White House reportedly is prepared to claim executive privilege over Bolton’s testimony and prepared for a lengthy court fight on that issue.

Hawley said Friday that “it’s just a fact” that calling witnesses would lead to prolonged legal drama in the courts.

Senate Minority Leader Charles E. Schumer and other Democrats contend that any White House lawsuit wouldn’t get too far in the courts.

What is less clear is how long such a fight might take, even if the courts expedite it.

“If the subpoenas are voted on bipartisan, and signed by the chief justice, I don’t think courts are going to mess with that,” Schumer said Tuesday. “And everyone knows that Trump’s claims for executive privilege — which he’s never really issued — in terms of immunity are so absolute that they’re almost meaningless.”