MI HB4470

Adds the Mackinac Bridge (portions not open to or intended for public use) to the list of "key facilities" where unauthorized entry is prohibited under Michigan's penal code

Unauthorized entry onto a key facility remains a felony punishable by up to 4 years imprisonment, a fine of up to $2,500, or both

Removes the requirement that a key facility must be "completely enclosed" for the trespassing prohibition to apply, while retaining the requirement for physical barriers and posted signage

Establishes that leaving a barrier open during normal operating hours for official business is not a valid defense against prosecution for unauthorized entry

Maintains existing protections for lawful assembly, peaceful petitioning, and labor disputes between employers and employees