Final answer:
The decision requiring states to draw U.S. Congressional districts with approximately equal population is based on the one-person-one-vote principle from Reynolds v. Sims (1964). Redistricting follows each decennial U.S. Census to ensure equal representation and prevent malapportionment. Gerrymandering, or drawing districts to favor certain parties, is illegal if it lessens minority voting strength.
Step-by-step explanation:
The decision that requires each state to draw its U.S. Congressional districts so that they are approximately equal in population is rooted in the one-person-one-vote principle established by the Supreme Court's decision in Reynolds v. Sims (1964). This decision reinforced the requirement that legislative districts, including those for the U.S. House of Representatives, must have roughly equal populations to ensure that every person's vote carries the same weight. Redistricting is the process by which the boundaries of these districts are redrawn, and it occurs every ten years following the collection of data from the U.S. Census. Adjustments are made to accommodate population shifts and maintain equal representation. These changes are imperative to comply with the principle of equal protection under the law and to prevent malapportionment.
During the redistricting process, some states may engage in gerrymandering, which involves drawing district lines to benefit a particular political party or group. However, practices that diminish the voting strength of minorities or target specific groups are prohibited under the Voting Rights Act and may be declared illegal.
In accordance with the U.S. Constitution, reapportionment also takes place after the U.S. Census, potentially altering the number of Congressional seats allotted to each state based on changes in population. It's crucial that redistricting honors the equal population requirement to ensure fair and effective representation in the U.S. Congress.