Linwood Wayne Huff appeals his conviction and sentence for possession with intent to distribute crack cocaine. Huff claims: the district court erred by denying his motion to suppress based upon an illegal search and seizure; the requirement in United States Sentencing Guideline § 3El.l(b), which states that a third-level of reduction for acceptance of responsibility can only be given upon motion by the Government, violates the separation of powers doctrine; the Government’s refusal to move for that third-level reduction was based on an unconstitutional motive; and the district court plainly erred in sentencing him under a mandatory, as opposed to advisory, Guidelines system.

The denial of a motion to suppress is reviewed under a two-tiered standard of review: factual findings are reviewed for clear error, issues of law de novo. E.g., United States v. Villalobos, 161 F.3d 285, 288 (5th Cir. 1998). Huffs constitutional challenges are reviewed de novo. E.g., United States v. Romero-Cruz, 201 F.3d 374, 377 (5th Cir.), cert. denied, 529 U.S. 1135, 120 S.Ct. 2017, 146 L.Ed.2d 965 (2000). As noted, Huff concedes that his claim that his sentence violates the Sixth Amendment is reviewed for plain error only.

*699 The investigatory stop and frisk of Huff did not violate his Fourth Amendment rights. Among other things, there was no unconstitutional seizure. See United States v. Shabazz, 993 F.2d 431, 436 (5th Cir. 1993). Officer Goodman was able to corroborate the anonymous tip, thereby providing Goodman with the requisite reasonable suspicion to justify the stop. And, Goodman had a reasonable belief that Huff was armed and dangerous, which justified the frisk. See United States v. Reyes, 349 F.3d 219, 224 (5th Cir. 2003); United States v. Rodriguez, 835 F.2d 1090, 1092 (5th Cir. 1988).

Huffs constitutional challenge, based upon separation of powers, to U.S.S.G. § 3E1.1(b) is moot in the light of United States v. Booker, — U.S. —, 125 S.Ct. 738, 160 L.Ed.2d 621 (2005). We reject Huffs contention that the Government’s refusal to move for a third-level credit for acceptance of responsibility was based on an unconstitutional motive. Huffs suppression hearing was the substantive equivalent of a full trial, requiring the Government’s full preparation; and, therefore, the Government was justified in not moving for the additional credit. U.S.S.G. § 3El.l(b); cf. United States v. Gonzales, 19 F.3d 982, 984 (5th Cir.), cert. denied, 513 U.S. 887, 115 S.Ct. 229, 130 L.Ed.2d 154 (1994).

Finally, Huff has not established, that but for the district court’s plain error in sentencing him under the mandatory Guidelines regime held unconstitutional in Booker, the outcome of his proceedings would likely have been different. See United States v. Mares, 402 F.3d 511, 521 (5th Cir. 2005), petition for cert, filed, (U.S. 31 Mar. 2005) (No. 04-9517). In this regard, the district court sentenced Huff to the high-end of the applicable range to achieve the desired punishment.

AFFIRMED