http://www.nybooks.com/articles/2018/05/24/crooked-trump-legal-swamp/
The legal route to holding Trump criminally liable for Cohen’s actions lies in the law of conspiracy. Since Cohen acted as a fixer for Trump, investigators could discover that on some occasions he acted criminally on Trump’s behalf. If so, a prosecutor could charge that Cohen and Trump were engaged in a criminal conspiracy, defined as an agreement to commit crimes in concert. Once two or more people have agreed to the general plan of action, any crime committed to advance the conspiracy counts as a crime for which both are criminally responsible—even if one acts without the other’s knowledge. For example, if Trump and Cohen criminally agreed to intimidate Stormy Daniels, and Cohen arranged for her to be threatened, then Trump could be charged with that threat, even if he did not know anything about it.
To make matters worse for Trump, there is little he can do to thwart the new investigation. Unlike the Mueller investigation, which Trump could end himself, the Cohen investigation in the Southern District would be extremely difficult for the White House to shut down. Trump could in principle fire the US attorney, a political appointee who serves at his pleasure, and appoint someone new with orders to end the Cohen inquiry. The civil servant prosecutors of the Southern District, however, cannot be fired except for misconduct. The strong tradition of prosecutorial independence means that, even if ordered to stop their investigation by Trump or a new US attorney, they would very likely treat such direction as itself a criminal obstruction of justice and find a way to keep digging.
Nor can Trump end the inquiry just by pardoning Cohen. All that would mean is that prosecutors would be able to force Cohen to testify by issuing a subpoena against him. Technically, Cohen could not invoke his Fifth Amendment right not to incriminate himself, because he would not be in jeopardy of a criminal conviction after the pardon. If Cohen refused to submit to the subpoena, he could be jailed for contempt of court—to which the pardon would not apply.
Federal prosecutors, then, could ultimately gather sufficient evidence to charge Donald Trump with crimes related to campaign contributions, structuring financial transactions, money-laundering, or conspiracy. These would be ordinary crimes, not connected to Russian election interference, not investigated by Mueller, and not anticipated when the FBI investigation of the 2016 election began.
These possible charges raise two pressing questions. May a sitting president be criminally indicted and tried for his crimes while in office? And may a president be impeached for criminal conduct that occurred before his presidency and had nothing to do with it?
