Regardless of the theoretical interpretation of this amendment, the practical effects thus far have been quite clear -- responsibilities and rights not handled by the federal government are left up to state and local governments. One of the most important areas in which this can be seen in action is through the investigation of crime. Because the federal government does not prohibit any state or locality's rights in searching a person or their property for evidence of a crime (other than the provisions of the fourth amendment), local police have the authority granted to them by their own state and/or local governments to search -- it is a right held in reserve by the people. This does not mean that local police (or federal agents, for that matter) have full reign in searching for evidence. Various matters of police abuse have been raised and debated over the centuries, but among the most profound was the legalized racism that many state and local laws allowed their police forces to practice. Based on federal laws, citizenship was not always a rigidly defined concept, and this allowed certain states and localities (specifically those in the South leading up to and following the Civil War) to deny certain protections and rights to individuals. The Fourteenth Amendment, passed after the close of the Civil War, addresses this issue: "All persons born or naturalized in the United States and subject to the jurisdiction thereof, are citizens of...

No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States" (FindLaw 2009). This quite clearly limits states' rights in many matters.
One of these matters is that of police searching. The Fourteenth Amendment affords all of the protections that the federal government provides to its citizens to all people living within the United States and "subject to its jurisdiction." This means that local and state law enforcement agents, while still granted their authority by their own local governments, are restrained in many of their actions by the provisions of the federal government (FindLaw 2009). Even if a state or locality passed a law granting broader authority for searching persons and personal property, the Fourteenth Amendment would preclude that law, making it unconstitutional and therefore unenforceable. The Fourteenth Amendment basically adds limitations to the rights of the states granted by the Tenth Amendment.

References

FindLaw (2009). "U.S. Constitution: Fourteenth Amendment." http://caselaw.lp.findlaw.com/data/constitution/amendment14/

Source Watch (2006). "U.S. constitutional amendment process." http://sourcewatch.org/index.php?title=U.S._constitutional_amendment_process

Tenth Amendment Center. http://www.tenthamendmentcenter.com/tenth-amendment-talking-points/