Marijuana laws are enforced by State and Federal governments.
The States usually prosecute most marijuana offenses. However, the Federal government will often opt to prosecute when acts involved Federal property (i.e. U.S. Forests), large quantities (over 50 plants or 50 kilos), the crossing of national borders, and where the investigation was conducted by Federal agents. Over 100 plants is mandatory 5 year sentence!
Sentencing guidelines are considered excessive, not only by defense attorneys, but by many Federal Judges. These guidelines are followed and enforced!