Trump's odds of silencing Comey: Executive privilege can't be used to cover up government misconduct
Legal experts said Trump would face an uphill climb if he asserted executive privilege to stop Comey from testifying before the congressional committee.
Trump likely would argue that Comey's testimony involves confidential conversations or matters of national security. But that claim would be undercut by the fact that the president has publicly discussed and tweeted about his conversations with Comey, said Rozell.
Trump faces another hurdle if he tries to block Comey's testimony. If Trump pressured Comey to drop the Flynn investigation, as Comey is expected to testify, then Trump may have engaged in obstruction of justice, according to some lawyers. Executive privilege cannot be used to "cover up government misconduct," said Andrew Wright, a professor at Savannah Law School.
http://www.reuters.com/article/us-usa-trump-russia-factbox-idUSKBN18T1OB