What was extortion at common law
At common-law extortion was where a public official knowingly threatened to use or used official acts (similar to a robber threatening to use or using violence) to obtain property not solely for the benefit of the Government. It was like a bribe. It was selling influence in official acts. It was an anti-corruption law.
What is a threat
A threat is "or else". Pay me or else I will... For example pay me or else I will take or withhold an official act and prosecute you for crime.
Difference between robbery and extortion
A robber threatens to use or uses violence to obtain property. Nobody is allowed to negotiate with violence, so obtaining property with violence is robbery. Extortion on the other hand is where a public official threatens to use or uses official acts to obtain property for third party benefit. The reason why obtaining property solely for the benefit of Government is not extortion is because the harm of extortion focuses on public corruption.
Difference between blackmail and extortion
Blackmail is different than extortion because at common law a blackmailer was a private person and not a public official.
Historic Courts of law
At common-law a court of law obtained property from one person and gave it to another. Therefore Courts of law required juries because juries do not use official acts. This is why an action for replevin was in a Court of law and not a court of equity, because the jury would obtain property and give it to another.
Courts of equity
At common-law a court of equity enforced property rights and therefore a chancery would take or withhold official acts and enforce property rights. This is why specific performance was in a court of equity, rather than in a court of law. The chancery would enforce the contract, which is a right of any kind, whatever, or property. So the chancery was enforcing property rights, not obtaining property rights.
If a police officer was called to the scene of an alleged assault, believed there was an assault, and arrested the accused on behalf of the claimaint did the police officer obtain rights? Or did the police officer just help enforce rights because the claimaint would have the right to make a citizen's arrest if her statement were true.
But if instead the police officer said to the accused pay the claimaint property or else I will take or withhold an official act and arrest you, is this okay? Or would this be an extra-judicial punishment inflicted by the police officer on the accused because he obtained property with accusations of crime without the accused receiving nor waiving his right to a trial?
Any private person (and a fortiori a peace officer) that is present when any felony is committed, is bound by the law to arrest the felon; on pain of fine and imprisonment, if he escapes through the negligence of the standers by. And they may justify breaking open doors upon following such felon: and if they kill him, provided he cannot be otherwise taken, it is justifiable; though if they are killed in endeavoring to make such arrest, it is murder. R v. Asante-Mensah,  2003 SCC 38
What do the Courts say today about the extortion laws?
The Supreme Court of Canada said in R v. Davis,  3 SCR 759
At common-law extortion was a "separate public official offense punishing the conduct of public officials who sought personal financial gain under colour of their office. It has since been statutorily expanded in some jurisdictions, such as Canada, to include more familiar forms of blackmail." .
The Supreme Court of the United States said in Evans v. United States, 504 U.S. 255 (1992)
At common law, extortion was an offense committed by a public official who took 'by colour of his office' money that was not due to him for the performance of his official duties. A demand, or request, by the public official was not an element of the offense. Extortion by the public official was the rough equivalent of what we would now describe as 'taking a bribe.' .
Is this ancient law still valid law today?
As we explained above, our construction of the statute is informed by the common-law tradition from which the term of art was drawn and understood. We hold today that the Government need only show that a public official has obtained a payment to which he was not entitled, knowing that the payment was made in return for official acts.
Without Reasonable Justification or Excuse
In Canada there is a reasonable justification or excuse clause contained within the extortion statutes. In the United States, the threat needs to be one of force, or under color of official right.
Justification is one of the easiest concepts to grasp, but most misunderstood in the legal community because lawyers are willfully blind to their own crimes. Justification is simply do you have the right. So a property owner would be justified in carrying away his property, but not another person's property. A person with permission from the rightful owner to use property would be justified in using property if they did so in accordance with their permission.
A person is justified in saying to their employer pay me or else I will stop working for you. An employer is justified in saying to a person work for me, or else I will stop paying you.
A public official is justified in saying pay the Government or else the Government will enforce its property rights against you. A public official is not justified in saying pay my friend or else the Government will enforce its property rights against you.
Under Color of Official Right
Color is the same as without justification. Color is using somebody else's property or right, without permission. So for example a public official using official acts to obtain property not solely for the benefit of Government would be color. The Supreme Court said color is crossing the line between public and private beneficiaries. In Wilkie v. Robbins, 551 U.S. 537 (2007)
the Supreme Court of the United States said:
The importance of the line between public and private beneficiaries for common law and Hobbs Act extortion is confirmed by our own case law, which is completely barren of an example of extortion under color of official right undertaken for the sole benefit of the Government.
Whaley was about a charge of extortion against a justice of the peace who wrongfully ordered a litigant to pay compensation to the other party as well as a small administrative fee to the court. Because the case involved illegally obtaining property for the benefit of a private third party, it does not stand for the proposition that an act for the benefit of the Government alone can be extortion.
It is the crime of extortion under the color of official right for a public official to obtain a right of any kind whatever for private third-party benefit. This simple law is violated everyday by the legal community, which has turned the criminal justice system into a racket where prosecutors threaten criminal prosecutions unless defendants pay.
Extortion is more odious than robbery, for robbery is apparent and hath the face of crime, whereas extortion puts on the visure of virtue.