U.S. Code as of: 01/06/03
Section 1505. Obstruction of proceedings before departments, agencies, and committees
Whoever, with intent to avoid, evade, prevent, or obstruct compliance, in whole or in part, with any civil investigative demand duly and properly made under the Antitrust Civil Process Act, willfully withholds, misrepresents, removes from any place, conceals, covers up, destroys, mutilates, alters, or by other means falsifies any documentary material, answers to written interrogatories, or oral testimony, which is the subject of such demand; or attempts to do so or solicits another to do so; or
Whoever corruptly, or by threats or force, or by any threatening letter or communication influences, obstructs, or impedes or endeavors to influence, obstruct, or impede the due and proper administration of the law under which any pending proceeding is being had before any department or agency of the United States, or the due and proper exercise of the power of inquiry under which any inquiry or investigation is being had by either House, or any committee of either House or any joint committee of the Congress -
Shall be fined under this title or imprisoned not more than five years, or both.
In other words, it's a crime to obstruct a congressional inquiry by harming a witness, punishable by 5 years in jail. The president, as chief law enforcement officer of the land, has the power to enforce this LAW by preventing it from being broken. In addition, if the Congress wants to find a witness in contempt by referring it to the US Atty, of course, they always can, but in the Schiavo case, this is a more expeditious way to perform the executive function.
Whoever corruptly, or by threats or force, or by any threatening letter or communication
Where has Greer done this? He simply issued an Order stating the Subpoenas changed nothing and did not affect his ruling. So, he hasn't communicated his obstruction in any manner.
the due and proper exercise of the power of inquiry under which any inquiry or investigation is being had by either House, or any committee of either House or any joint committee of the Congress -
Did you fail to read the "due and proper exercise of the power of inquiry". First, the law that I cite for a contempt of congress finding is not inconsistent with that language. Second, Greer in his Order states that the subpoenas were not a due and proper exercise of the House's power of inquiry.
A crime, in this case, has not occurred until Congress passes the contempt resolution. Until they do so, I stand by my statement that the President cannot enforce the subpoenas.