Federal prison and congressional testimony
<p>Assume an individual has been convicted and sentenced for United States Federal crimes and is serving his sentence in the appropriate Federal prison.</p>

<p>Then, he is subpoenaed to testify, under oath, before some Congressional committee(s) in public session. The prisoner is willing to testify.</p>

<p>Must the prison authorities make the prisoner available to travel to the Capitol?</p>

<p>Or:
   Can they substitute making the prisoner available at a suitable facility at the prison?</p>

<p>Or:   Can they say they'll get back to Congress at the completion of the individual's sentence?</p>

<p>Congress has the power to issue subpoenas, and it does not go through the courts. That power is extremely broad and courts generally resist attempts to interfere with Congress's constitutional power under the Speech or Debate Clause – "for any Speech or Debate in either House, they shall not be questioned in any other Place" – (which the courts interpret as including inquiries and subpoena powers enabling such inquiries, <a href="https://supreme.justia.com/cases/federal/us/421/491/" rel="nofollow noreferrer">Eastland v. United States Servicemen's Fund</a>, 421 U.S. 491), but may intervene in the case of extreme violation of constitutional rights (<a href="https://law.justia.com/cases/federal/appellate-courts/F2/521/1024/70367/" rel="nofollow noreferrer">McSurely v. McClellan</a>, 521 F.2d 1024). As stated in <a href="https://openjurist.org/589/f2d/582/exxon-corporation-v-federal-trade-commission-corporation" rel="nofollow noreferrer">Exxon Corp. v. FTC</a>, 589 F.2d 582,</p>

<blockquote>
  <p>the courts will intervene to protect constitutional rights from
  infringement by Congress, including its committees and members...
  where constitutional rights are not violated, there is no warrant for
  the judiciary to interfere with the internal procedures of Congress</p>
</blockquote>

<p>There does not seem to be any overriding federal law pertaining to the Bureau of Prisons and Congressional subpoenas which says that the authorities must respond in a certain way to a Congressional subpoena, forcing authorities to resist or comply in a certain way. The only issue would be whether the subpoena is lawful, and given the breadth of Congressional subpoena power, it is extremely unlikely that such a subpoena would <em>not</em> be held by the courts to be legal. Congress certainly could take into consideration the option of delaying a hearing for a few years, and there is zero chance that they actually would do so. In other words, the authorities must comply with the subpoena.</p>

<p>If the authorities do not comply with the subpoena, the responsible individual can be the subject of a contempt resolution. If passed, then the sergeant-at-arms of either house can arrest the violator and he can theoretically be held in the Capitol jail for the remainder of the legislative session. Or, the Senate can, under its rules, seek a court order forcing compliance. Or, the presiding officer of the House or Senate can refer the matter to the District Attorney for DC, for prosecution as criminal contempt under <a href="https://www.law.cornell.edu/uscode/text/2/192" rel="nofollow noreferrer">2  USC 192</a>.</p>

united-states congress prison subpoena