The Overview

Driving across the Mackinac Bridge is still fine, but wandering into the parts that aren't meant for the public could now land you in prison for up to four years. Michigan's new law makes it a felony to enter or remain without permission in the parts of the Mackinac Bridge not open to or intended for public use, putting those areas in the same protected "key facility" category as power plants, refineries, and other covered sites. The law updates Michigan's criminal code, and breaking it is a felony punishable by up to four years in prison, a fine of up to $2,500, or both. It took effect immediately when it was filed with the Secretary of State on July 23, 2026, and violators face criminal prosecution under state law.

The Francis Scott Key Bridge in Baltimore collapsed in March 2024 after the container ship Dali struck it, an event that drew national attention to the vulnerability of major bridges. The National Transportation Safety Board recommended that owners of 68 bridges in 19 states assess how vulnerable their structures are, and it named the Mackinac Bridge among those warranting review.

Under the new law, a covered facility must be enclosed by a physical barrier and posted with clearly visible signs, placed so at least one can be seen from any point of entry. The law preserves the right to lawful assembly and peaceful petitioning, including during labor disputes. Lead sponsor Senator John Damoose introduced the bill Feb. 11, 2025; cosponsors include Senators Dan Lauwers, Jon C. Bumstead, Michael Webber, Lana Theis, Rick Outman, Rosemary Bayer, and John Cherry.

The Debate

The Michigan Senate passed the bill on March 13, 2025, 36 to 0, with one member excused. The Michigan House passed the bill on July 3, 2026, 96 to 12, with two members not voting, and gave it immediate effect.

Damoose told Upper Michigan's Source that existing penalties were inadequate: "The penalties for trespassing on the bridge are basically a civil infraction with a small fine." Kim Nowack, executive director of the Mackinac Bridge Authority, told Upper Michigan's Source: "We look forward to it, we hope it will be a deterrent for anybody who's thinking of doing this, that it will be a felony charge if they are caught trespassing on the Mackinac Bridge."

What's Next

No state agency has to sign off or write new rules before the law can be enforced. The Michigan Senate Fiscal Agency described the cost to the state as small and hard to pin down but gave no dollar estimate, and the law sets aside no money for signs or enforcement. The law does not say who must put up or maintain the required signs in the bridge's non-public areas.

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