Huh? Can you just quote the actual wording you are referencing.
The federal government is still limited to only those powers expressly delegated to it in the U.S. Constitution. Yes, I know it does a gazillion other things nowadays. Pretty much everything(I estimate 90%) the federal government does nowadays is unconstitutional and certainly outside of the intentions of the framers in 1787.
This is the Preamble, establishing the purpose of the US Constitution:
We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defence, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America.
This is Article I, Section 8, Clause 18:
To make all Laws which shall be necessary and proper for carrying into Execution the foregoing Powers, and all other Powers vested by this Constitution in the Government of the United States, or in any Department or Officer thereof.
This is how murder can be a federal crime.