Detroit-Windsor Border Overview

Last verified: April 2026

The Most Cannabis-Consequential Crossing in North America

The Detroit-Windsor border is the most cannabis-consequential international crossing in North America — not because cannabis is legal on both sides (it is) but because the federal government on the U.S. side treats every kilometer of border as Schedule I terrain.

The Crossings

Trade Volume Context

The Detroit-Windsor corridor has historically been the busiest international border crossing in North America by trade volume, carrying roughly 27% of all merchandise trade between the United States and Canada. The Ambassador Bridge recorded 3.5 million passenger crossings and 1.9 million commercial truck crossings in 2025 — about 5.4 million total, per Bridge and Tunnel Operators Association data cited by CBC News.

The 2025 Sarnia Surprise

Notably, in 2025 the Blue Water Bridge in Sarnia surpassed the Ambassador Bridge in commercial truck volume for every month of 2025 — 2.1 million versus 1.9 million crossings — marking the first time the Ambassador Bridge lost its top spot for cross-border truck traffic. Higher Ambassador tolls and re-routing pressures explain the shift. The Sarnia surprise reshapes the broader Detroit-area logistics economy and shifts some cross-border commercial pressure away from Detroit’s congestion.

Cannabis Crosses Neither Way

Canada legalized recreational cannabis nationally in October 2018 under the Cannabis Act, and Ontario operates a regulated retail and online market. Despite that, bringing cannabis across the border in either direction is a federal crime under the U.S. Controlled Substances Act and Canadian Customs Act.

The official CBP statement: “crossing the border or arriving at a U.S. port of entry in violation of this law may result in denied admission, seizure, fines, and apprehension.”

Lifetime Inadmissibility for Non-Citizens

For non-U.S. citizens, the consequences extend far beyond a seizure. Under Section 212(a)(2)(A)(i)(II) of the Immigration and Nationality Act, an admission of having committed a controlled-substance offense — including past cannabis use — is grounds for inadmissibility to the United States, potentially for life. CBP officers may ask about cannabis use. Lying to a CBP officer is a separate federal offense with even harsher consequences. See Lifetime Inadmissibility.

Cross-Border Commuter Reality

For Windsor commuters who work in Detroit (an estimated 5,000 cross daily for work) and U.S. citizens who travel into Ontario for cannabis dispensary visits, the practical advice is unanimous among border attorneys:

• Do not carry cannabis across the border in any direction, including CBD with any THC content
• Do not admit to past cannabis use unless required to under a specific question; you have the right to revoke a request to enter and turn back
• Assume CBP officers can search phones, laptops, and social-media activity at the border with broad Fourth Amendment latitude
• Non-U.S. citizens with any cannabis-industry employment, ownership, or investment should consult a Canadian and U.S. immigration attorney before crossing

The Five Crossings in Detail

Ambassador Bridge

Opened 1929; privately owned by the Moroun family’s Detroit International Bridge Company. Passenger and commercial truck traffic. 3.5M passenger + 1.9M commercial truck crossings in 2025. See Ambassador Bridge.

Detroit-Windsor Tunnel

Opened 1930; passenger vehicles only (no commercial trucks). One-way toll: US$9. See Detroit-Windsor Tunnel.

Michigan Central Railway Tunnel

Opened 1910; rail freight only. Operated by Canadian Pacific Railway and CSX.

Gordie Howe International Bridge (Planned)

Spring 2026 planned opening. ~$5.7B CAD (~$5B USD). 6 lanes plus the first non-special-event legal pedestrian crossing of the Detroit River. Toll set at US$5.75 (with 25% NEXUS discount). As of April 2026, ~3,300 systems tests in progress; not yet open. See Gordie Howe Bridge.

Blue Water Bridge (Sarnia)

Opened 1938 / 1997 (twin span). Sarnia-Port Huron crossing, north of Detroit. 2.1M commercial truck crossings in 2025 — surpassed the Ambassador Bridge for the first time.

Casino Tourism & the Border

The Detroit-Windsor casino corridor — MGM Grand Detroit, MotorCity Casino Hotel, Hollywood Casino at Greektown (formerly Greektown Casino) on the U.S. side, Caesars Windsor across the river — operates under strict no-cannabis-on-property regimes on both sides. Crossing for casino tourism is common; crossing with cannabis is not advisable in either direction.