In the last 30 years, Congress has been feverishly adding new crimes to the federal criminal code. Now, it is criminalizing acts that are already criminal. State laws make it a crime to threaten, intimidate or kill witnesses in state criminal proceedings. However, the State Witness Protection Act, introduced by Pennsylvania Senator Robert Casey, would make these acts separate, federal crimes in cases where the defendant crosses state lines, or uses interstate commerce facilities (such as mail or phone) in furtherance of the crime. Why the need to make federal crimes of acts that are already state crimes? For one thing, the new bill would give federal prosecutors the authority, effectively, to intervene in state prosecutions. And the new bill would ratchet up the penalties - it imposes a minimum penalty of 20 years, and 30 years in cases of attempted murder. And while it is politically difficult to take issue with efforts to be "tough on crime," this law would impose significant costs, further blurring the line between state and federal responsibility, and by further taxing a prison system that already jails more people than any other country in the world. Absent a compelling federal interest in supervising state prosecutions in this way, Congress would be wiser to let the states protect their own witnesses.