Okay, here is the question.

Has there been an opinion by the US Supreme Court that might be read by the defense bar as allowing or even endorsing jury nullification?
Specifically, that a jury charge is only advisory.

I haven't seen that specifically but it is often phrased in terms of the jury being "judges" of the facts and/or the law. Different states empower juries differently. In Texas, juries are fact-finders but law recievers. See TCCP 36.13. Compare e.g. Ind. Const., Art. 1, §19 (In all criminal cases whatever, the jury shall have the right to determine the law and the facts.)

This case has some good starting points. Jones v. United States, 526 U.S. 227, 248, n. 8 (1999)

Looks to me like such an argument would be contrary to established law as recently stated in Merced v. McGrath (Ninth Circuit October 18, 2005):

A juror's ability to acquit "in the teeth of both law and facts", Horning v. District of Columbia, 254 U.S. 135, 138(1920), is a well-established power that defense counsel correctly
observed "ha[s] been with us since Common Law
England." Merced, 114 Cal. Rptr. 2d at 784; see also Bushell's Case, 124 Eng. Rep. 1006 (C.P. 1670) (releasing jury foreman Bushell, who was arrested for voting to acquit
William Penn of unlawful assembly against the weight of the evidence and the requirements of the law). Importantly, while jurors have the power to nullify a verdict, they have no right
to do so. See Standefer v. United States, 447 U.S. 10, 22-23(1980) (citations omitted). If jurors had a right to nullify, then a court would have a correlative duty to safeguard their ability to exercise this right. See Wesley Newcomb Hohfeld, Some Fundamental Legal Conceptions as Applied in Judicial Reasoning,23 Yale L.J. 16, 32 (1913) (describing a legal taxonomy in which a duty is the correlate of a right). But courts manifestly do not have a duty to ensure a jury's free exercise of this power. See, e.g., United States v. Powell, 955 F.2d 1206, 1213 (9th Cir. 1992) (holding that courts have no duty to provide nullification instructions to juries); United States v. Dougherty, 473 F.2d 1113, 1136-37 (D.C. Cir. 1972) (same). In fact, "it is the duty of juries in criminal cases to take the law from the court, and apply that law to the facts as they find them to be from the evidence." Sparf v. United States, 156 U.S. 51, 102 (1895).

The power to nullify is reenforced by a jury's freedom from recrimination or sanction for exercising this power after the verdict has been reached. See United States v. Thomas,
116 F.3d 606, 615 (2d Cir. 1997) "in addition to the courts duty to safeguard the secrecy of the jury deliberation room . . . the several rules protecting the unassailability of jury verdicts of acquittal . . . serve to permit juries to acquit out of compassion or compromise or because of their assumption of a power which they had no right to exercise, but to which they
were disposed through lenity." (quoting Standefer, 447 U.S. at 22). Notwithstanding the unassailability of jury verdicts of acquittal, inasmuch as no juror has a right to engage in nullification;and, on the contrary, it is a violation of a juror's sworn duty to follow the law as instructed by the court;trial courts have the duty to forestall or prevent such conduct, whether by firm instruction or admonition or, where it does not interfere
with guaranteed rights or the need to protect the
secrecy of jury deliberations, . . . by dismissal of an offending juror from the venire or the jury. Id. at 616.

[This message was edited by Martin Peterson on 11-06-05 at .]