http://www.law.umkc.edu/faculty/projects/ftrials/conlaw/powers13th14th15th.htm
Exploring Constitutional Conflicts
The Powers of Congress to Enforce the 13th, 14th, and 15th Amendments 
The Issue: How far is Congress, under the Civil War Amendments, allowed to go in regulating what it sees as violations of equal protection, due process, and other basic liberties?
Introduction
In the Civil Rights Cases (1883), the Supreme Court considered the constitutionality of a civil rights act, enacted eight years earlier, that was remarkably broad in scope. The 1875 act banned racial discrimination in many types of public accomodations, including hotels, railroad cars, theaters, and amusement parks. If the 1875 act had been upheld and enforced, the United States would have had a much happier history. Not until 1964 would such sweeping civil rights legislation again make it through Congress. In the Civil Rights Cases, the Court found that neither Section 2 of the 13th Amendment nor Section 5 of the 14th Amendment empowered Congress to ban private discrimination. Writing for the Court, Justice Bradley concluded that the discrimination in public accomodations had "nothing to do with slavery or involuntary servitude" and therefore fell outside of the power granted Congress in the 13th Amendment, while Section 5 of the 14th Amendment allowed Congress to regulate only discrimination in which the state was an actor. In dissent, Justice John Harlan argued that the denial of equal public accomodations constituted a "badge of slavery" that Congress could prohibit under its 13th Amendment power. Moreover, Harlan argued that with respect to discrimination in public accomodations, the discriminating individuals or corporations acted as "agents of the state." 
Jones vs Alfred H. Mayer Co. (1968) arose when the developer of a surburban St. Louis subdivision refused to sell Joseph Jones a home because he was black. Jones sued the developer, alleging a violation of 42 U.S.C. 1982 which granted "all citizens of the United States...the same right as is enjoyed by white citizens...to purchase...real property." The Court rejected the developer's argument that Congress lacked the power under Section 2 of the 13th Amendment to ban private discrimination in housing. According to the Court in Jones, so long as Congress could rationally conclude that private discrimination in the housing market was "a badge of slavery," the statute should be upheld. 
In South Carolina vs Katzenbach (1966), the Court considered a challenge to provisions of the 1965 Voting Rights Act. South Carolina objected to provisions that required that South Carolina (and other southern states with small percentages of of enrolled minority voters from among those eligible to vote) to submit to the Attorney General for "preclearance" changes in state voting laws. The Court found the preclearance provision to be a constitutional exercise of the power of Congress under Section 2 of the 15th Amendment. The Court saw the power of Congress as broad enough to allow creation of specific mechanisms for carrying out the general prohibition (the ban on denying the vote on account of race) of the 15th Amendment. 
Another provision of the 1965 Voting Rights Act was at issue in Katzenbach v. Morgan. The Court considered whether the Constitution gave Congress the power to ban literacy tests, a device long used to deny the vote to non-whites. Although the Court had previously determined literacy tests to not violate the Equal Protection Clause, the Court nonetheless founf that the power of Congress under Section 5 of the 14th Amendment was broad enough to authorize the literacy test ban. The Court seemed to see Section 5 as giving Congress the power to add to--but not subtract from--protections that the Court finds contained in the 14th Amendment. A somewhat narrower interpretation of Morgan is that the Court will defer to findings of Congress that purport to establish that an applicable legal standard (relating, e.g., to equal protection) is met--even when deferring to those factual findings effectively overrules Supreme Court precedent. 
In Oregon v. Mitchell (1970), the Court rejected some of the broad language of four years earlier in Morgan. The Court, in finding that Congress lacked the power to compel states to guarantee persons over the age of eighteen to vote in state elections, indicated that Section 5 of the 14th Amendment does not give Congress the power to enforce a broader interpretation of the reach of the 14th Amendment than given by the Supreme Court. Because the Court found the denial of the vote to 18 to 20 years olds not to offend the Equal Protection Clause, Congress lacked the power under Section 5 to legislatively mandate that states allow persons in that age group to vote. (The extension of the right to vote to eighteen-year olds in state elections was subsequently accomplished by the ratification of the 26th Amendment in 1971). Four dissenters argued that the Court was bound, under Morgan, to accept Congress's more generous interpretations of the reach of the 14th Amendment. 
In U. S. v Guest (1966), the U. S. attorney in Georgia brought a prosecution under Section 241 of the 1870 Civil Rights Act against persons for intimidating and filing false reports against blacks who attempted to integrate public facilities. Those charged argued that Section 241 (which made it illegal for two or more persons to conspire to intimidate "any citizen in the free exercise of any right or privilege secured to him by the Constitution") reached only state actors or, if it did intend to cover private actors, it was outside of the power of Congress. On the issue of whether the Constitution gave Congress the power to reach private discrimination, six justices suggested that it did--implying that an overruling of the Civil Rights Cases of 1883 was appropriate. 
In City of Rome v U. S. (1980), the Court upheld a decision of the Justice Department to reject a proposed change in Rome, Georgia's method of electing city commissioners. DOJ had rejected Rome's proposed change not based on any finding that the change was intended to discriminate against black voters, but because it had the discriminatory effect of making it more difficult for black candidates to be elected. Even though the Court's Equal Protection Clause jurisprudence teaches that the Clause prohibits only purposeful discrimination, not actions with discriminatory effects, the Court found Congress to have been acting within its Section 2 of the the 15th Amendment powers. The Court said it would defer to the judgment of Congress that because of past "ingenious defiance" of the right of black voters, it might be necessary to focus on discriminatory effects to uphold "the spirit" of the 15th Amendment. Justice Rehnquist, in his dissent, contended that the DOJ's action was not a valid exercise of Congress's Section 2 remedial powers. 
Two more recent Supreme Court decisions illustrate the Court's trend of reigning in congressional power. In 1997, in City of Boerne v Flores, the Court ruled that Religious Freedom Restoration Act (an Act intended to restrore the "compelling state interest test" for evaluating Free Exercise Clause claims that the Court discarded in its 1990 decision, Employment Division v Smith) was unconstitutional, at least as applied to state and local governments. The Court concluded that the Constitution, and in particular Section 5 of the Fourteenth Amendment, gave no power to Congress to do more than adopt remedial measures consistent with Fourteenth Amendment interpretations of the Court, and that Congress had instead tried to changed the substantive law--substituting its interpretation of the Free Exercise Clause for that of the Supreme Court. Finally, in U. S. vs Morrison (2000), invalidating the Violence Against Women Act's authorization of private federal suits for gender-motivated assaults, the Court held that Section 5 of the 14th Amendment--contrary to the suggestion of six justices in Guest--gave Congress no power to reach private discrimination. 
Constitutional Grants of Powers to Congress under the Civil War Amendments 
AMENDMENT XIII
Passed by Congress January 31, 1865. Ratified December 6, 1865. 
Section 1. 
Neither slavery nor involuntary servitude, except as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States, or any place subject to their jurisdiction. 
Section 2. 
Congress shall have power to enforce this article by appropriate legislation. 
AMENDMENT XIV
Passed by Congress June 13, 1866. Ratified July 9, 1868. 
Section 1. 
All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside. No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws. 
Section 2-4 [omitted]. 
Section 5. 
The Congress shall have the power to enforce, by appropriate legislation, the provisions of this article. 
AMENDMENT XV
Passed by Congress February 26, 1869. Ratified February 3, 1870. 
Section 1. 
The right of citizens of the United States to vote shall not be denied or abridged by the United States or by any State on account of race, color, or previous condition of servitude. 
Section 2. 
The Congress shall have the power to enforce this article by appropriate legislation. 
Questions
1. What would seem to be a better basis for upholding the public accomodations provisions of civil rights laws, the Commerce Clause or the enforcement powers granted to Congress in the Civil War amendments? 
2. It has been suggested that holding private discrimination outside the reach of the federal government serves several values: it enhances individual liberty (the choice of individuals not to associate with other individuals is respected), it reinforces pluralism and the principle of federalism. What do you think of these arguments? 
3. The 13th Amendment is unique in that by its own words it applies to private individuals as well as government. How far does Section 2 of the 13th Amendment go in allowing Congress to reach forms of private discrimination? If discrimination in housing can be "a badge of slavery," might also discrimination in the membership policies of a private club? How does one determine what is or is not a "badge of slavery" reachable by Section 2 of the 13th Amendment? 
4. In South Carolina v Katzenbach the Court says it will determine only whether Congress has chosen a "rational" means of enforcing its 15th Amendment powers. Do you agree that is the proper test? 
5. Katzenbach v Morgan suggests that Congress should be given the latitude to enforce a broader interpretation of the reach of the 14th Amendment than the Supreme Court has provided--Congress may add to, but not subtract from, the 14th Amendment rights recognized by the Court. Is this a sound view of Congress's 14th Amendment power, or do you favor the more restrictive interpretation adopted in the more recent cases of City of Boerne and Morrison? Why? 
6. What if Congress, contrary to the Court's holding in Roe v Wade, took the view that a fetus is "a person" for 14th Amendment purposes and, on that basis, prohibited states from enforcing laws authorizing abortions? Under the theory of Katzenbach v Morgan, would that be a valid exercise of Congress's 14th Amendment power? Why not? 
7. Robert Bork labeled Morgan "a revolutionary constitutional doctrine." He argued that it might authorize Congress to overturn any state law by simply finding that a state legislative classification violated the Equal Protection Clause? Is he right? 
8. If, in Oregon v Mitchell, the Court had upheld the federal law guaranteeing the right of eighteen-year-olds to vote in state elections, would logic have compelling the Court to also uphold a federal law giving the vote to seven-year-olds? 
9. Is Oregon v Mitchell consistent with Katzenbach v Morgan? 
10. Should U. S. v Guest be seen as overruling the Civil Rights Cases of 1883 on the question of whether the 14th Amendment allows Congress to ban private discrimination? 
11. Do you agree that it might be necessary to ban changes in voting laws that have discriminatory effects on a racial group in order to enforce the constitutional right of members of a racial group of not being purposefully denied the right to vote? 
12. Might the "compelling state interest" test of the Religious Freedom Restoration Act struck down as applied to states in City of Boerne still apply in cases where the free exercise of religion claim is asserted against federal authorities? What power in the Constitution might support this provision of RFRA? 
The Price ("Mississippi Burning") Case
In United States v Price et al (1966), the Supreme Court found that Congress, in the 1866 Civil Rights Act, reached private actors acting in concert with state officials to deprive persons of their constitutional rights. The Court overturned a decision throwing out the federal indictments brought against KKK members who participated with county officials in murdering three civil rights workers near Philadelphia, Mississippi in 1964. To read more about this fascinating case: 
The Mississippi Burning Trial <http://www.law.umkc.edu/faculty/projects/ftrials/price&bowers/price&bowers.htm>
Exploring Constitutional Conflicts Homepage <http://www.law.umkc.edu/faculty/projects/ftrials/conlaw/home.html>