MI HB5315

Amends MCL 750.552c to restructure the definition of "key facility" into two categories: facilities listed in subsection (3) that require only posting, and facilities in subsection (2)(b) that require both physical barriers and posting.

Designates specific bridges as key facilities requiring signage on non-public portions: any movable bridge in Michigan, Mackinac Bridge, Zilwaukee Bridge, Rouge River Bridge, MacArthur Bridge, and all international crossings including Ambassador Bridge, Blue Water Bridge, Detroit-Windsor Tunnel, Gordie Howe International Bridge, and International Bridge.

Maintains criminal penalties of up to 4 years imprisonment or $2,500 fine for intentionally entering or remaining on key facility premises without authority or permission.

Clarifies posting requirements by mandating minimum 1-inch letter height, minimum 50 square-inch sign size, and spacing to ensure at least one sign is visible at any entry point.

Adds new defense provision stating it is not a defense if a key facility designed to be enclosed has its barrier left open during normal operating hours, provided proper signage is posted.