Peggy Lou filed a lawsuit again "We Fix 'Em Rite," an auto body shop, for the sloppy paint job it did on her 1998 car. Once the lawsuit was filed with the appropriate clerk of court, Peggy Lou personally dropped a copy of the lawsuit in the mail. "We Fix 'Em" says it never received notice of the lawsuit. Local court rules require that a lawsuit be served by an independent process server or by the sheriff's department. Is this an example of substantive law or procedural law? Explain the difference.