Can a gag order prevent someone from testifying in a congressional hearing?
<p>In this article from the guardian - <a href="https://www.theguardian.com/us-news/2018/jan/16/steve-bannon-trump-congress-intelligence-questioning" rel="nofollow noreferrer">https://www.theguardian.com/us-news/2018/jan/16/steve-bannon-trump-congress-intelligence-questioning</a> it has been mentioned that,  former white house aide, Steve Bannon is claiming that he is unable to testify because white house told him not to do so and so leaders from democratic party are claiming that a gag order has been used to stop him from testifying to the the House Intelligence Committee.</p>

<p>Isn't it unconstitutional to do so? unless gag order has been given to prevent any kind of leak which may lead to risk associated with national security, which is not the case here? And ultimately who has the final authority to issue a gag order?</p>

<p>There is a legal doctrine of executive privilege, where the executive branch can resist subpoenas, but that privilege is limited (<a href="http://caselaw.findlaw.com/us-supreme-court/418/683.html" rel="nofollow noreferrer">US v. Nixon</a>).</p>

<blockquote>
  <p>Neither the doctrine of separation of powers nor the generalized need
  for confidentiality of high-level communications, without more, can
  sustain an absolute, unqualified Presidential privilege of immunity
  from judicial process under all circumstances.</p>
</blockquote>

<p>SCOTUS pointed to the kinds of cases where such privilege would be valid</p>

<blockquote>
  <p>Absent a claim of need to protect military, diplomatic, or sensitive
  national security secrets, the confidentiality of Presidential
  communications is not significantly diminished by producing material
  for a criminal trial under the protected conditions of in camera
  inspection, and any absolute executive privilege under Art. II of the
  Constitution would plainly conflict with the function of the courts
  under the Constitution.</p>
</blockquote>

<p>But otherwise,</p>

<blockquote>
  <p>when a claim of Presidential privilege as to materials subpoenaed for
  use in a criminal trial is based, as it is here, not on the ground
  that military or diplomatic secrets are implicated, but merely on the
  ground of a generalized interest in confidentiality, the President's
  generalized assertion of privilege must yield to the demonstrated,
  specific need for evidence in a pending criminal trial and the
  fundamental demands of due process of law in the fair administration
  of criminal justice</p>
</blockquote>

<p>Decades later, Harriet Miers claimed executive immunity (as White House counsel) to a subpoena to testify before the Committee on the Judiciary, and the <a href="https://www.courtlistener.com/opinion/1810993/committee-on-jud-us-house-of-repres-v-miers/" rel="nofollow noreferrer">district court ruled</a> rebuffed that claim</p>

<blockquote>
  <p>There are powerful reasons supporting the rejection of absolute
  immunity as asserted by the Executive here. If the Court held
  otherwise, the presumptive presidential privilege could be transformed
  into an absolute privilege and Congress's legitimate interest in
  inquiry could be easily thwarted.</p>
  
  <p>if the Executive's absolute immunity argument were to prevail,
  Congress could be left with no recourse to obtain information that is
  plainly not subject to any colorable claim of executive privilege.</p>
</blockquote>

<p>However, executive privilege <em>has</em> been invoked dozens of times since Nixon – there are no other SCOTUS decisions.</p>

<p>We should set aside current political posturing. POTUS might claim executive privilege, and then the question is whether the courts would order Banon to testify. We don't know the basis for such privilege, but we can assume that it would involve national security issues (thus might be within the penumbra of the Nixon ruling). Traditionally, executive privilege has involved the person who <em>is</em> president, not the person who <em>ended up becoming</em> president, so it would be extremely surprising if the courts upheld immunity in a pre-election matter.</p>

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