The phrase "the riot act" is often used to describe a warning or admonition given to someone who is out of line or behaving poorly. Synonyms for this phrase include "a stern talking-to", "a firm rebuke", "a reprimand", "a dressing-down", and "a chastisement". These words all convey a sense of seriousness and urgency, and are often used in situations where someone has crossed a line or failed to follow rules or expectations. When dealing with difficult or unruly individuals, it can be helpful to have a variety of synonyms for "the riot act" at your disposal, in order to get your message across clearly and effectively.