“Three years ago, Virginia and the nation watched horrified as civil protest was marred by violence and hate,” Mr. Northam said in his emergency declaration, adding, “We must take all precautions to prevent that from ever happening again.”

The governor warned that tens of thousands of people could converge on the State Capitol on Monday, which is a federal holiday, Martin Luther King’s Birthday.

Democrats won both houses of the General Assembly in November, taking full control of state government in part based on their promises to enact gun control measures. Among the issues under consideration: background checks for gun owners, a red flag law that would allow the authorities to take firearms away from people deemed dangerous to themselves or others, and the potential to limit gun purchases to one per month.

The proposals have sparked a backlash across the state. Dozens of municipalities have declared themselves “Second Amendment sanctuaries,” where local officials have vowed to oppose any new gun control measures, and advocates who oppose gun restrictions are organizing bus rides to the State Capitol on Monday.