The main people who would be responsible for enforcing the money laundering laws and detecting money laundering would be the people at the Financial Crimes Enforcement Network (FinCEN).
They would then enforce the law and notify FBI agents or even local police where the money laundering is happening at.
The local police or the FBI would then make the arrest of the person if caught money laundering and then the person would go to the local jail where they'd see a judge in court who would then decide on the case and prosecute the person for money laundering.
If convicted of money laundering the person faces from 5 to 15 years in prison and in some cases could face 20 to 25 years in prison for money laundering.