Section 37A. The mayor of any city other than a city having a Plan D or Plan E form of charter, the city manager of a city having a Plan D or Plan E charter, and the selectmen of a town, hereinafter called the city or town official, may, if satisfied that a riot or other form of civil disorder is occurring or there is a danger that it may occur, and that a curfew is necessary for the public safety in such city or town, impose a curfew in all or part or parts of such city or town. Such curfew shall be imposed by a formal proclamation of the existence or threat of riot or other form of civil disturbance in the city or town and the need of a curfew to protect the public safety. Said proclamation shall be in writing and shall set forth all the conditions of such curfew. No curfew shall take effect until two hours after the issuance of the proclamation declaring the imposition of such curfew.

Such curfew may restrict or prohibit the movement or presence of persons, vehicles and animals in or on public ways and places, including areas to which the public has a right of access, and also places of amusement and entertainment, vacant lots and other open areas, provided that reasonable exceptions are made for all persons having business of an emergency nature which requires the use of public ways. When such curfew is imposed, the city or town official shall immediately use all reasonable and practicable means to inform all persons in such city or town of such curfew and its conditions, such as by the conspicuous posting of notices in public places, announcement by sound-powered voice or other such device, publication in newspapers of general circulation in such city or town and announcement over radio and television stations serving such city or town. While such curfew is in effect, its terms may be modified in any manner not inconsistent with this action by proclamation of said officials; provided, that two hours advance notice shall be given and that such modifications are publicized in the manner required in this section.

The city council or the town meeting, as the case may be, shall have the authority to revoke or modify and such curfew. Any curfew imposed by a city or town official under this section shall, unless sooner terminated by proclamation of said city or town official or by action of the city council or the town meeting or by the governor as hereinafter provided, terminate seventy-two hours from the hour it takes effect. Upon the termination of such curfew, additional curfews may be imposed in accordance with the provisions of this section.

The governor, acting under chapter six hundred and thirty-nine of the acts of nineteen hundred and fifty, as amended, or any other law granting him special powers during periods of emergency, may modify or revoke any curfew imposed under this section.

Any person knowing or having reason to know of such curfew who violates any conditions thereof shall be punished by imprisonment for not more than six months or a fine of not more than five hundred dollars, or both. Such person may be arrested without a warrant and kept in custody for not more than twenty-four hours, Sundays and holidays excepted, at or before the expiration of which time he shall be taken before a proper court or magistrate and proceeded against according to law.

Nothing in this section shall be construed to limit or supersede the power of cities and towns to impose curfews by appropriate ordinances or by-laws.