The federal state of Bremen bans Reich and Reich war flags in public.
A corresponding decree will come into force next Monday, as the city's interior authorities announced.
According to the information, the police law will be supplemented by a provision that prohibits the public display and use of the historical flags.
Officials are allowed to confiscate the flags in the event of violations, the owners face a future fine of up to 1,000 euros.
Bremen's Interior Senator Ulrich Mäurer (SPD) described the flags as "symbols of National Socialist and xenophobic sentiments" that should be banned from the public.
"It was time to act," he said, referring to the recent demonstrations against the measures to contain the corona pandemic in Berlin, where right-wing extremists waved the flags of the German Empire in front of the Reichstag.
The Reich and Reich war flags have long been regarded as a symbol of identification of right-wing extremists, Reich citizens and other opponents of democracy.
Unlike swastika flags and similar National Socialist badges, they are not prohibited.
So far there have only been provisions that the police can confiscate them in certain cases, for example during demonstrations.
In the decree, according to the Bremen interior authorities, the ban is justified by the fact that showing the black-white-red flags "represents a lasting impairment of the requirements for an orderly civic coexistence and thus a danger to public order".
It applies to all variants of the Reich War Flag.
The simple imperial flag is only affected if "there is a specific provocation effect in the individual case".