But Capt. Greg Shipley, a spokesman for Maryland State Police, said on Monday that Maryland has had a strict gun-control law on the books since 1966.
"The fact that a portion of the Brady Law was struck down will not impact us because it's already state law," he said.
Shipley said that state police have conducted checks since the state law was passed. It prohibits people from owning handguns if they have been convicted of felonies and some misdemeanors or have a record of mental illness. Recently, he said, people convicted of domestic violence were added to the list.
Shipley said the state performs about 31,000 checks each year and has prevented 15,000 ineligible people from buying weapons since 1966.
Officials in Franklin and Fulton counties in Pennsylvania said they have no plans to stop enforcing the law. Franklin County Sheriff Robert Wollyung said he did not agree with the premise of the sheriffs who challenged the law.
"I'm not going to stop doing them," he said.
Wollyung said his office checks the criminal backgrounds of about 1,500 potential gun buyers a year. He said state law prohibits checking medical records unless officials have specific knowledge about an individual.
Fulton County Chief Deputy Sheriff Nancy Suders said her office conducts between 20 and 30 checks each month.
"Until we're told otherwise, we'll continue to do it," she said.
Sgt. Tim Allue, a spokesman for the Pennsylvania State Police, said state police have examined the record of sale in gun purchases for the last 50 years.
"We'll continue to do that," he said.
If officials discover a gun buyer has a criminal record, he said they immediately notify the local police agency. He said the state conducted 177,363 such checks in 1995.
What's more, Allue said officials expect an instant-check computer system to be running by next spring or summer.
West Virginia State Police spokesman Sgt. Thomas Barrick said police conduct checks from 12 locations throughout the state. He said the state averages about 25,000 checks a year and denies about 1 percent of potential buyers.
Barrick said state's attorneys will review the court's decision.
"Until that point, we will carry on business as usual," he said.
Gun-control advocates predicted the Supreme Court ruling will have little impact on most communities since law enforcement agencies will face intense pressure to keep guns out of the hands of criminals.
Robin Terry, a spokeswoman for Handgun Control Inc., which lobbied for passage of the Brady Law, said "one or two rogue sheriffs" would "find themselves in a sea of controversy."
"You have to remember, it's law enforcement who lobbied for this law because it helps them prevent crime," she said.