Presumption that Statutory Constriction is the domain of Judicary

"Similarly, when the appellant challenges a judgment call on a topic on which "the agency has been entrusted with wide discretion by the General Assembly," we will overturn the decision only if it can be fairly characterized as  "arbitrary or capricious" and thus a "clear abuse of delegated discretion."
[ Vasaio v. Dep't of  Motor Vehicles, 42 Va. App. 190, 196-97, 590 S.E.2d 596, 599 (2004) (citations omitted).]
 On the other hand, an "agency does not possess specialized competence over the  interpretation of a statute merely because it addresses topics within the agency's delegable  authority." 
[Finnerty v. Thornton Hall, Inc., 42 Va. App. 628, 634, 593 S.E.2d 568, 571 (2004);  see also 7-Eleven, Inc. v. Dep't of Envtl. Quality, 42 Va. App. 65, 73, 590 S.E.2d 84, 88 (2003) (en banc).]
Pure statutory construction, a matter within the "core competency of the judiciary,"  
[Finnerty, 42 Va. App. at 635, 593 S.E.2d at 571, requires de novo review. Mattaponi Indian Tribe, 43 Va. App. at 707, 601 S.E.2d at 675 (citation omitted). 
"This axiom stems from basic principles of separation of powers. 'It is emphatically the province and duty of the judicial department to say what the law is.'" 
[Finnerty, 42 Va. App. at 635, 593 S.E.2d at 571 (quoting Marbury v. Madison, 5 U.S. (1 Cranch) 137, 177 (1803)).]
 It necessarily follows that the a priori question whether the statute delegates or withholds discretion is itself a question of statutory interpretation, one implicating our duty of de novo review."
 - Citland Ltd. v. Attorney General Kilgore, 45 Va. App. 268, 610 S.E.2d 310 (2005).