CHARLOTTESVILLE, VA. ? A recurring thought while wading through Judge Anna Diggs Taylor’s truly appalling opinion in ACLU v. NSA was the old Latin proverb, Ignorantia juris non excusat – “ignorance of the law is no excuse.”

Judge Taylor either chose to ignore or is actually oblivious to a number of important legal precedents that are incompatible with her decision – a decision that is certain to be reversed on appeal.

While the case raises several important issues, the most important is whether the Fourth Amendment’s prohibition against “unreasonable searches and seizures” prohibits the president from directing the National Security Agency during time of congressionally authorized war from monitoring communications between known or suspected enemy operatives abroad and people inside the United States without a judicial warrant.

Judge Taylor asserts that the Fourth Amendment “requires prior warrants for any reasonable search, based upon prior-existing probable cause.”

This ignores a long line of Supreme Court decisions holding, as the court explained in the 2002 case of Board of Education v. Earls, that a search “unsupported by probable cause” may be “reasonable” when “special needs, beyond the normal need for law enforcement, make the warrant and probable-cause requirement impracticable.”

These “special needs” cases authorize customs inspectors to search our baggage and vehicles when we cross into the United States, permit police to set up sobriety checkpoints on streets and highways, and allow health and safety inspectors to search restaurants, factories producing hazardous waste, and other commercial establishments where safety is a concern without the slightest bit of “probable cause” to believe a law is actually being broken.

An even more obvious example would be the searches passengers endure before being permitted to board an airplane, searches that would obviously be unconstitutional by Judge Taylor’s theory – leaving us defenseless against terrorists who might want to sneak weapons on board.

On some issues, she can’t even plead ignorance of the law, as she correctly sets out the law and then ignores it. For example, she notes that under the “state secrets privilege,” a court must dismiss a case if the “very subject matter of the action” is a state secret.

While, obviously, the details of America’s efforts to monitor the communications of Osama bin Laden and his terrorist associates are quite properly highly classified, in response to leaks published in The New York Times our government has acknowledged that a terrorist surveillance program does exist and that it intercepts communications by foreign terrorist outside this country even when they communicate with people within the United States, who might well be foreign nationals aligned with al-Qaida.

Judge Taylor reasons that the existence of the program is no longer classified, and thus the case can go forward to trial on the merits. That the government will be precluded from defending its actions by explaining the program without compromising sensitive national security information doesn’t trouble her.

She ignores the fact that the test of “reasonableness” under the Fourth Amendment requires, as the Supreme Court reaffirmed in Earls, “balancing the nature of the intrusion on the individual’s privacy against the promotion of legitimate governmental interests.” And the Supreme Court in Haig v. Agee observed that no governmental interest is more compelling that the national security.

Judge Taylor also ignores a long history of support for independent presidential power to authorize warrantless foreign intelligence wiretaps, including a 1968 act of Congress, Carter administration Atty. Gen. Griffin Bell, and every federal court of appeals to consider the issue.

About the only useful aspect of her decision in ACLU v. NSA may be to remind us of the dangers inherent when federal judges decide to pursue their own policy preferences rather than be governed by the rule of law.