The piggyback statutes are not themselves mandatory minimums but sentence offenders by reference to underlying statutes including those that impose mandatory minimums. The Guidelines denied judges sentencing discretion. Constitutional Boundaries

Defendants sentenced to mandatory minimum terms of imprisonment have challenged them on a number of constitutional grounds beginning with Congress's legislative authority and ranging from cruel and unusual punishment through ex post facto and double jeopardy to equal protection and due process. Mandatory minimums implicate considerations under the Eighth Amendment's cruel and unusual punishments clause. The clause bars mandatory capital punishment statutes. The clause does bar imposition of a mandatory life term of imprisonment upon a juvenile. Thus, the lower federal courts have regularly upheld mandatory minimum statutes when challenged on separation of powers grounds, and the Supreme Court has denied any separation of powers infirmity in the federal sentencing guideline system which at the time might have been thought to produce its own form of mandatory minimums. Drug Crimes

Federal law regulates the cultivation, manufacture, distribution, export, import, and possession of certain plants, drugs, and chemicals, which it designates as controlled substances and classifies according to medicinal value and potential for abuse under the Controlled Substances Act and the Controlled Substances Import and Export Act. It suggested that the escalator approach in some instances might be unduly severe. The mandatory minimums, imposed in addition to the sentence imposed for the underlying crime of violence or drug trafficking, vary depending upon the circumstances: (1) imprisonment for not less than 5 years, unless one of higher mandatory minimums below applies; (2) imprisonment for not less than 7 years, if a firearm is brandished; (3) imprisonment for not less than 10 years, if a firearm is discharged; (4) imprisonment for not less than 10 years, if a firearm is a short-barreled rifle or shotgun or is a semi-automatic weapon; (5) imprisonment for not less than 15 years, if the offense involves the armor piercing ammunition; (6) imprisonment for not less than 25 years, if the offender has a prior conviction for violation of Section 924(c); (7) imprisonment for not less than 30 years, if the firearm is a machine gun or destructive device or is equipped with a silencer; and (8) imprisonment for life, if the offender has a prior conviction for violation of Section 924(c) and if the firearm is a machine gun or destructive device or is equipped with a silencer. (4) "Congress should consider clarifying the statutory definitions of the underlying and predicate offenses that trigger mandatory minimum penalties under section 924(c) and the Armed Career Criminal Act to reduce the risk of inconsistent application and the litigation that those definitions have fostered." First, they argue that their sentences are disproportionate to their offenses. The current array includes the following:
A majority of the judges responding to a Sentencing Commission survey thought that the mandatory minimum sentences for production and distribution of child pornography and other child exploitation offenses were generally appropriate. Persons other than individuals may, however, incur criminal liability as conspirators. The federal conspiracy statute outlaws conspiracy to commit any federal crime, including aggravated identity theft. 851(a), if they elect to ask the court to sentence a defendant under the three strikes provision. Without such notice, the court may not impose an enhanced sentence.
Federal mandatory minimum sentencing statutes limit the discretion of a sentencing court to impose a sentence that does not include a term of imprisonment or the death penalty. They have a long history and come in several varieties: the not-less-than, the flat sentence, and piggyback versions. Federal courts may refrain from imposing an otherwise required statutory mandatory minimum sentence when requested by the prosecution on the basis of substantial assistance toward the prosecution of others. First-time, low-level, non-violent offenders may be able to avoid the mandatory minimums under the Controlled Substances Acts, if they are completely forthcoming.
The most common imposed federal mandatory minimum sentences arise under the Controlled Substance and Controlled Substance Import and Export Acts, the provisions punishing the presence of a firearm in connection with a crime of violence or drug trafficking offense, the Armed Career Criminal Act, various sex crimes including child pornography, and aggravated identity theft.
Critics argue that mandatory minimums undermine the rationale and operation of the federal sentencing guidelines which are designed to eliminate unwarranted sentencing disparity. Counter arguments suggest that the guidelines themselves operate to undermine individual sentencing discretion and that the ills attributed to other mandatory minimums are more appropriately assigned to prosecutorial discretion or other sources.
State and federal mandatory minimums have come under constitutional attack on several grounds over the years, and have generally survived. The Eighth Amendment's cruel and unusual punishments clause does bar mandatory capital punishment, and apparently bans any term of imprisonment that is grossly disproportionate to the seriousness of the crime for which it is imposed. The Supreme Court, however, has declined to overturn sentences imposed under the California three strikes law and challenged as cruel and unusual. Double jeopardy, ex post facto, due process, separation of powers, and equal protection challenges have been generally unavailing.
The United States Sentencing Commission's Mandatory Minimum Penalties in the Federal Criminal Justice System (2011) recommends consideration of amendments to several of the statutes under which federal mandatory minimum sentences are most often imposed.
This is an abbreviated version of CRS Report RL32040, Federal Mandatory Minimum Sentencing Statutes, stripped of its citations, footnotes, and appendixes.