The US Supreme Court today takes up the question of whether a person can be tried twice for the same offense -- a case with possible implications for President Donald Trump and the Russia probe.
The case involves Terance Gamble, who in 2008 was convicted of second-degree felony robbery.
Seven years later, Gamble was pulled over in Alabama for a traffic violation and found to be in possession of a gun. The state sentenced him to a year in prison because felons are barred from possessing firearms.
Federal authorities tried Gamble separately for the same gun offense and he was sentenced to four years in prison.
The Fifth Amendment of the US Constitution says that no one can be "twice put in jeopardy of life or limb" for the same crime.
But for more than 150 years, the court has held that being tried separately by a state and the federal government does not violate this principle because they are "separate sovereigns."
The Justice Department has set limits to avoid abuses in these cases and these are rare anyway, said Dane Ciolino, a law professor at Loyola University in New Orleans.
"A conviction by one sovereign usually results in loss in interest by the other," Mr Ciolino told AFP.
Yet if state authorities fail to win a conviction of a suspect, or drop charges, federal prosecutors often step in and go after the defendant -- or vice versa.
This was the case with Terry Nichols, one of the defendants in the bombing of a federal building in Oklahoma City in 1995. The attack killed 168 people.
After federal authorities failed to win a death penalty conviction, the state of Oklahoma put Nichols on trial. And again, Nichols was sentenced to life in prison because the jury was not unanimous on putting him to death.
Minor crimes like Gamble's are often subjected to more than one trial in violation of the spirit of the constitution, say jurists who support his appeal before the Supreme Court.
The American Civil Liberties Union has urged the court to drop its acceptance of double trials.
"With the ever-metastasizing federal criminal law -- there are now over 4,500 federal crimes on the books -- there is tremendous overlap with state law on everything from drug possession to tampering with an odometer," the ACLU said.
"This greatly increases the threat of duplicative prosecutions for a vast and increasing amount of conduct."
But other anti-racism advocacy groups are more cautious, such as the Thurgood Marshall Center, which argues that letting people be tried by both a state and the federal government has helped advanced the cause of African American rights. They say blacks are better defended by the feds.
For instance, federal authorities charged police officers suspected in the beating of black motorist Rodney King in Los Angeles in 1991 after a mainly white California state jury acquitted them. This last decision triggered nationwide riots.
Aside from the issue of civil rights, Ciolino said that if the Supreme Court ends up barring separate trials for the same crime, this could come into play in special counsel Robert Muller's probe of alleged collusion between the Trump campaign and Russia in the 2016 election and whether Trump has tried to obstruct the investigation into this relationship.
Trump has said he does not rule out pardoning his former campaign manager Paul Manafort, who faces prison time for violating federal fraud laws.
Under the current separate sovereigns doctrine, states such as New York or Virginia could bring charges against Manafort if Trump pardons him.
Such a pardon would be seen as Trump's way of encouraging other suspects in the Russia probe to decline to cooperate with Mueller, with the suggestion that if they hold fast, he will reward them with a pardon.
But if the court rules in favor of Gamble and no longer upholds more than one trial for one offense, a Trump pardon would stand pat.
In a display of how the issue crosses partisan lines, two of the nine judges on the court -- progressive Ruth Bader Ginsburg and conservative Clarence Thomas -- seem in favor of abandoning the "separate sovereigns" principle.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)