Now the question is whether the accused should be incarcerated pending appeal. That, in turn depends on 18 USC 3143, which provides in pertinent part:

(1) Except as provided in paragraph (2), the judicial officer shall order that a person who has been found guilty of an offense and sentenced to a term of imprisonment, and who has filed an appeal or a petition for a writ of certiorari, be detained, unless the judicial officer finds—
(A) by clear and convincing evidence that the person is not likely to flee or pose a danger to the safety of any other person or the community if released under section 3142 (b) or (c) of this title; and
(B) that the appeal is not for the purpose of delay and raises a substantial question of law or fact likely to result in—
(i) reversal,
(ii) an order for a new trial,

In the DC Circuit, a defendant who presents a "close question" of constitutional law which could result in reversal is considered to have raised a "substantial question of law" within the meaning of this statute.

The appropriate time to raise it is on consideration of the question of whether the accused should begin serving his sentence pending appeal.

Dr. Joyner, the flaw in your analysis is that there's no law establishing the "independent prosecutor's office" that Fitzgerald filled. And that's not the right terminology to describe his office, either; I don't mean to be pedantic, but the actually terminology matters here.

The "independent counsel" law under which prosecutors like Ken Starr or Lawrence Walsh were appointed was deliberately allowed to lapse by bipartisan agreement of lawmakers who believed it was a cure worse than the disease. (You'll probably recall that there were serious constitutional challenges mounted to the statute that permitted such appointments, although those were beaten back in the Supreme Court.)

Since then, there has been an internal regulation of the Department of Justice, duly codified in the Code of Federal Regulations (28 C.F.R. part 600, which I blogged about at length back in 2005), under which "special counsel" could be appointed. That regulation, however, ultimately leaves such special counsel subject in important respects to the supervision and control of the Attorney General as the cabinet officer within the Executive Branch who exercises the delegated responsibility of law enforcement that the Constitution grants the President.

Fitzgerald's initial appointment, however, wasn't made pursuant to the special counsel regulation. Instead, his appointment purported to give him authority "independent of the supervision or control of any officer of the Department [of Justice]." Later, Acting AG Comey (acting in lieu of AG Ashcroft, who'd recused himself) expressly stated that "my conferral on you of the title of 'Special Counsel' in this matter should not be misunderstood to suggest that your position and authorities are defined and limited by 28 CFR Part 600." Why things were done this way is unclear; the most likely explanation is that Fitzgerald insisted upon it, but that may turn out in retrospect to have been profoundly unwise.

So with regard to your argument that "the constitutionality of federal law ought be accepted on face value until ruled otherwise," that's rather the Libby team's point: They don't think there is a federal law that authorized the appointment of Fitzgerald in this fashion, and it expressly was done outside of the restrictions via regulation that are very arguably essential in order for the appointment to be valid under constitutional separation of powers principles.

The legitimacy of Fitzgerald's appointment in this manner, moreover, is a pure question of law that doesn't depend on any factual determinations by the jury or Judge Walton. That's why it's a particularly strong potential appellate point, and therefore why it's particularly likely to satisfy the release-pending-appeal requirement that the Libby team have shown a "substantial question of law or fact" (in addition to showing that he's not dangerous or a flight risk).

And contrary to the implication of Big Tent's post, when a defendant has shown that he's no flight risk, not dangerous, isn't appealing for delay, and has raised at least one such "substantial question," then release pending appeal is mandatory, not discretionary.

The "independent counsel" law under which prosecutors like Ken Starr or Lawrence Walsh were appointed was deliberately allowed to lapse by bipartisan agreement of lawmakers who believed it was a cure worse than the disease. (You'll probably recall that there were serious constitutional challenges mounted to the statute that permitted such appointments, although those were beaten back in the Supreme Court.)

Since then, there has been an internal regulation of the Department of Justice, duly codified in the Code of Federal Regulations (28 C.F.R. part 600, which I blogged about at length back in 2005), under which "special counsel" could be appointed. That regulation, however, ultimately leaves such special counsel subject in important respects to the supervision and control of the Attorney General as the cabinet officer within the Executive Branch who exercises the delegated responsibility of law enforcement that the Constitution grants the President.

Fitzgerald's initial appointment, however, wasn't made pursuant to the special counsel regulation. Instead, his appointment purported to give him authority "independent of the supervision or control of any officer of the Department [of Justice]." Later, Acting AG Comey (acting in lieu of AG Ashcroft, who'd recused himself) expressly stated that "my conferral on you of the title of 'Special Counsel' in this matter should not be misunderstood to suggest that your position and authorities are defined and limited by 28 CFR Part 600." Why things were done this way is unclear; the most likely explanation is that Fitzgerald insisted upon it, but that may turn out in retrospect to have been profoundly unwise.

So with regard to your argument that "the constitutionality of federal law ought be accepted on face value until ruled otherwise," that's rather the Libby team's point: They don't think there is a federal law that authorized the appointment of Fitzgerald in this fashion, and it expressly was done outside of the restrictions via regulation that are very arguably essential in order for the appointment to be valid under constitutional separation of powers principles.

The legitimacy of Fitzgerald's appointment in this manner, moreover, is a pure question of law that doesn't depend on any factual determinations by the jury or Judge Walton. That's why it's a particularly strong potential appellate point, and therefore why it's particularly likely to satisfy the release-pending-appeal requirement that the Libby team have shown a "substantial question of law or fact" (in addition to showing that he's not dangerous or a flight risk).