The House Government Oversight Committee has wide latitude when it comes to issuing subpoenas, as specified in its own rules:
(d) Authorize and issue subpoenas as provided in House Rule XI, clause 2(m), in the conduct of any investigation or activity or series of investigations or activities within the jurisdiction of the Committee;
And, House Rule XI clause 2(m) further clarifies that the Chair has the right:
(B) to require, by subpoena or otherwise, the attendance and testimony of such witnesses and the production of such books, records, correspondence, memoranda, papers, and documents as it considers necessary.
We may wonder whether there are any exceptions to this power of subpoena, but it would seem there are not:
Should a witness deliberately mislead the committee by falsifying either verbal or written testimony, the penalties are grave:
In an administration where truth has become collateral damage, I can imagine a scenario where one after another of its key players could be subpoenaed before the House Government Oversight Committee and forced to testify under oath. Even Trump can be subpoenaed about his conflicts of interests and his ties to Russia. If he lies, he can be dispatched to prison for a minimum of 5 years. If he tells the truth, we will at last know what, if any, crimes have been committed. Since Jason Chaffetz seems rusty at performing his duty as chair of this powerful committee, I suggest he issue his first subpoena to KellyAnn Conway, who does not know how to tell the truth. He can hone his prosecutorial skills on her, and then extend his inquiry to Bannon, Flynn, and, ultimately, the President himself.
To focus his investigations on “who leaked the damaging information” instead of who actually did the damage is an abdication of his responsibility. If he does not want to do his job, he should resign and let a patriot take over.