US SB477

Reduces quantity thresholds triggering mandatory minimum sentences for fentanyl offenses by 95%: from 400 grams to 20 grams and from 40 grams to 2 grams for higher penalties, and from 100 grams to 5 grams and from 10 grams to 0.5 grams for lower thresholds

Expands coverage to include both "scheduled or unscheduled" fentanyl analogues, closing a loophole for novel synthetic variants not yet formally scheduled

Directs the U.S. Sentencing Commission to review and amend federal sentencing guidelines within 120 days to align with the new thresholds, using emergency rulemaking authority

Requires the U.S. Postal Service to increase deployment of chemical screening devices (mass spectrometers, Raman spectrophotometers, etc.) to detect fentanyl in mail and express shipments

Authorizes $9,000,000 for USPS to acquire screening equipment and staff scientists during all operational hours for fentanyl interdiction