The crime of false swearing occurs when a person “makes a false statement, which he or she knows to be false, under an oath required or authorized by law.” False swearing is a gross misdemeanor. RCW 9A.72.040.
False swearing charges can occur if you are denied a firearm purchase. The dealer is required to report the denial to law enforcement and the police may investigate and refer the denial to the local prosecutor for charging. By charging you with false swearing, the prosecutor essentially alleges that you lied on the application to purchase the firearm.
However, it is imperative that you consult with a knowledgeable firearms lawyer to determine your liability for false swearing charges. You may have been wrongfully denied the firearm purchase, which would be a defense to any false swearing charges.