The 4th Circuit Court of Appeals ruled that police officers can frisk anyone to determine if a person is armed regardless of whether he is lawfully carrying a weapon, setting up a potential Supreme Court showdown.

The appeals court's opinion appears to challenge a 6th Circuit Court of Appeals opinion from 2015, setting up a conflict that likely will need to be resolved by the Supreme Court.

At issue is whether police frisks run afoul of the Fourth Amendment's protection against unreasonable search and seizure and the standard set out by the Supreme Court in Terry v. Ohio in 1968. A Terry frisk is a justifiable search for weapons, including in the absence of probable cause, so long as there is suspicion that an individual is armed and dangerous.

The 4th Circuit ruled that "traffic stops alone are inherently dangerous for police officers" in U.S. v. Shaquille Montel Robinson on Monday.

Police received a tip that Robinson was in a parking lot often used for drug-trafficking activity and had just concealed a loaded firearm in his pocket before getting in a vehicle. Police stopped the vehicle because the passengers weren't wearing seatbelts and frisked Robinson, which led to the discovery of his weapon and arrest for the possession of firearm by a felon.

Robinson contended in court that the frisk violated his Fourth Amendment rights because he said the officers had no reason to think he was dangerous. A lower court disagreed. The 4th Circuit ruled traffic stops are inherently dangerous and said, "traffic stops of persons who are armed, whether legally or illegally, pose yet a greater safety risk to police officers."

In Shawn Northrup v. City of Toledo Police Department in 2015, however, the 6th Circuit ruled that police cannot frisk, disarm and detain every gunman who lawfully possesses a firearm.

"While open-carry laws may put police officers (and some motorcyclists) in awkward situations from time to time, the Ohio legislature has decided its citizens may be entrusted with firearms on public streets," the 6th Circuit said in its opinion. "The Toledo Police Department has no authority to disregard this decision — not to mention the protections of the Fourth Amendment — by detaining every "gunman" who lawfully possesses a firearm. ... And it has long been clearly established that an officer needs evidence of criminality or dangerousness before he may detain and disarm a law-abiding citizen."

The 6th Circuit noted that in places where it is legal to have a firearm, unlawful possession "is not the default status," making the suspicion or knowledge that a person has a firearm difficult to equate with evidence of danger.

That sets up a conflict between the 6th Circuit saying that the police need to establish evidence of danger and the 4th Circuit's opinion that a traffic stop is inherently dangerous.

Texas Supreme Court Justice Don Willett, who is on Trump's short list for the Supreme Court nomination, tweeted that he thinks the issue is headed for review by the high court.