US election laws are a mainly left up to the individual states because the Constitution delegates broad election-related powers to the states. The federal government can create certain election laws that all states must adhere to, however these laws are generally limited to only specific protections outlined by the Constitution.
First off, according to the Tenth Amendment, the federal government's powers are limited to only what is delegated to it by the Constitution:
The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.
So, if the Constitution doesn't imply that the federal government can do something, then it's generally up to the state governments to handle it.
For election laws, the relevant powers are outlined in numerous articles and amendments. Here are few examples of powers granted to the individual states:
- Article One describes how representatives are simply chosen by 'the people' of each state, and senators were originally chosen by state legislatures:
The House of Representatives shall be composed of Members chosen every second Year by the People of the several States, and the Electors in each State shall have the Qualifications requisite for Electors of the most numerous Branch of the State Legislature.
The Senate of the United States shall be composed of two Senators from each State, chosen by the Legislature thereof, for six Years; and each Senator shall have one Vote.
- Article Two describes how presidential electors are appointed in whatever way a state legislature 'may direct':
Each State shall appoint, in such Manner as the Legislature thereof may direct, a Number of Electors, equal to the whole Number of Senators and Representatives to which the State may be entitled in the Congress: but no Senator or Representative, or Person holding an Office of Trust or Profit under the United States, shall be appointed an Elector.
As you can see, originally the Constitution delegates broad powers to the states to handle federal elections. However, several articles and amendments define some protections that the state election laws needed to follow, and give the federal government the power to make laws to enforce them:
- As mentioned above, Article One gave states some broad powers to decide how members of Congress are elected, however Section 4 of Article One also gives Congress the power to make laws covering the 'time' or 'manner' of those congressional elections:
The Times, Places and Manner of holding Elections for Senators and Representatives, shall be prescribed in each State by the Legislature thereof; but the Congress may at any time by Law make or alter such Regulations, except as to the Places of chusing Senators.
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 power to enforce this article by appropriate legislation.
- The Seventeenth Amendment changed the way that senators were elected to match that of the representatives, thus taking some of the power away from the state legislatures:
The Senate of the United States shall be composed of two Senators from each State, elected by the people thereof, for six years; and each Senator shall have one vote. The electors in each State shall have the qualifications requisite for electors of the most numerous branch of the State legislatures.
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 sex.
Congress shall have power to enforce this article by appropriate legislation.
Section 1. The right of citizens of the United States to vote in any primary or other election for President or Vice President, for electors for President or Vice President, or for Senator or Representative in Congress, shall not be denied or abridged by the United States or any State by reason of failure to pay any poll tax or other tax.
Section 2. The Congress shall have power to enforce this article by appropriate legislation
Section 1. The right of citizens of the United States, who are eighteen years of age or older, to vote shall not be denied or abridged by the United States or by any State on account of age.
Section 2. The Congress shall have power to enforce this article by appropriate legislation.
There are some other articles/sections/amendments that cover election stuff, but you can see how the Constitution typically defines where the federal government can make election laws: it outlines a topic or protection that must be respected across the country, and explicitly gives Congress the power to make and enforce laws that guarantee those protections.
So, to sum it all up: election laws in the US are mainly handled by the individual states because the Constitution gives them broad powers to do so, either explicitly in various articles or more broadly through the Tenth Amendment. There are a few areas where the federal government can enforce election laws across all of the states, but these areas are fairly limited in scope so most of the power still rests in the hands of each state.
x
is allowed since that is the default - it's more correct to ask whyx
is not forbidden. Removing freedoms from people, companies, associations, cities, or states is something that requires a strong argument for intervention. If working solutions exist that do not require removing freedoms and restricting activity then the American system is likely to leave the status-quo to be.