The constitutionality of a sentence is a question of constitutional law. Questions of constitutional law are subject to plenary review by this Court and the district court's interpretation of the law is reviewed for correctness. State v. Webb, 2005 MT 5, ¶ 8, 325 Mont. 317, 106 P.3d 521 (analyzing whether a mandatory minimum sentence violated a defendant's procedural and substantive due process rights under the United States and Montana Constitutions); State v. LaFreniere, 2008 MT 99, ¶ 7, 324 Mont. 309, 180 P.3d 1161 (analyzing whether a condition added to defendant's probation violated the ex post facto clauses of the United States and Montana Constitutions).
A district court's resolution of an issue involving a question of constitutional law during sentencing is a conclusion of law which we review to determine whether the court's conclusion is correct. State v. Killam, 2005 MT 255, ¶ 7, 329 Mont. 50, 122 P.3d 439.