Now that law enforcement in America have killed a suspect remotely, it's important to consider the legality of the decision—and what might happen next time.

State laws generally allow law enforcement to legally use lethal force against a suspect if he or she poses an "imminent threat" to the officer or other innocent parties, which is underscored by a standard of whether the force is "proportional and necessary." A 1985 Supreme Court case called Tennessee v. Garner allows for deadly force if a fleeing suspect poses "a significant threat of death or serious physical injury to the officer or others."

Does the means of killing matter for that legal standard? In this case, probably not, according to several legal experts I spoke to. The bomb disposal robot that turned into an improvised remotely triggered killing machine wasn't autonomous and can, in this instance, be looked at as a tool that was used to diminish the threat suspect Micah Johnson posed to Dallas police officers.

"It might be justified to use remotely controlled robots to apply lethal force where such force is justified," Jay Stanley, a senior legal analyst at the American Civil Liberties Union told me. "As a legal matter, the choice of weapon in a decision to use lethal force does not change the constitutional calculus, which hinges on whether an individual poses an imminent threat to others, and whether the use of lethal force is reasonable under the circumstances."