We conclude that McCormick waived his first argument in the
proceedings below. We review the validity of waiver de novo.
Blanco de Belbruno v. Ashcroft, 362 F.3d 272, 278 (4th Cir.
2004). A waived issue is not reviewable on appeal, even for
plain error. United States v. Robinson, 744 F.3d 294, 298 (4th
Cir. 2014). What is required to effect valid waiver varies
depending on the right at issue, United States v. Olano, 507
U.S. 725, 733 (1993), but as relevant here, “[a] party who
identifies an issue, and then explicitly withdraws it,” such as
by raising and withdrawing an objection, “has waived the issue.”
Robinson, 744 at 298 (4th Cir. 2014) (quoting United States v.
Rodriguez, 311 F.3d 435, 437 (1st Cir. 2002)). Indeed, “[t]here
can be no clearer intentional relinquishment or abandonment of a
known right than when the court brings the defendant’s prior
objection to his attention,” and the defendant confirms his
intention to withdraw. United States v. Carrasco-Salazar, 494
F.3d 1270, 1273 (10th Cir. 2007) (citation omitted).
McCormick does not contend, nor could he, that he did not
withdraw his objection to the court’s finding that the offense
involved a large-capacity firearm. Instead, he argues that his
withdrawal was neither knowing nor voluntary because the
district court did not engage McCormick in an extensive colloquy
regarding “his willingness to withdraw his objection.” Reply