New lords new laws.

When authority changes hands, the rules often change with it. A new ruler, owner, or leadership group may impose different expectations, policies, and priorities on those subject to its control.

The saying also conveys the disruption felt by people who must adapt to each incoming authority. It can be used resignedly or critically, especially when changes in power bring fresh demands rather than continuity.

Use it when a change of leadership is followed by altered rules or procedures. It suits discussions of governance, institutions, workplaces, or households, and may imply that subordinates have little choice but to adjust.