Under color of authority: A legal phrase used in the United States indicating a person is claiming or implying the acts he or she is committing are related to and legitimized by his or her role as an agent of governmental power, especially if the acts are unlawful.
I would agree that any crime by federal officials pretending they have the authority to infringe upon our individual right to keep and bear arms should be prosecuted to the fullest extent of the law. As a juror, I would send the jack-booted thug responsible for such a crime to maximum security for the longest lawful sentence. “I was just following orders” is not an acceptable excuse - neither from the agent on the street or the immediate subordinate of the petty tyrant issuing an executive order for a gun grab.
Do federal law enforcement agents not have to swear to uphold the Constitution? If they are, then they are breaking their oath of office, just like His Lordship, and they should face the full consequences of such an action.