It rejected the government's argument that such a charge was valid under an "American common law of war".
The judges rejected the Justice Department's argument that the charge was nevertheless valid under an American "common law of war" and because Congress had listed the crime as an offense for the tribunals in a 2006 statute.
They debated various legal strategies, such as filing tort claims and, more dubiously, claiming that as a sovereign person under common law, a court without a jury does not have jurisdiction over them.
Mair was charged with murder, which is a crime under common law and not an offence under counter-terrorism legislation; and the jury was only to be asked to decide whether or not Mair had committed the crime of murder.
There is nothing novel about the law taking into account a criminal's state of mind; one of the prerequisites for a conviction under common law is "mens rea" — a guilty mind, malice aforethought, criminal intent.
In December, the Supreme Court agreed to take a case in which states and allied land trust organizations have charged that greenhouse gases emitted by a few big power companies constitute a "nuisance" under common law.
In other pollution cases, the Supreme Court has supported suits claiming that pollution caused harm as a "nuisance" under common law, most often interpreted to prohibit noise and light pollution.
Incitement, on the other hand, is an offence under the common law, and covers situations where an individual encourages another person to engage in activities which will result in a criminal act taking place, and intends for this act to occur.
Thomas C. Goldstein, arguing for the defendant, told the justices that under English common law, an illegal arrest was considered a form of trespass.
