A bid to continue online council meetings until after 7 May has been rejected by the High Court.
Emergency legislation was passed in the Commons last year allowing councils to meet online due to coronavirus, but it ends the day after local elections.
Hertfordshire County Council applied to extend measures but it was dismissed.
Judges said primary legislation would be needed to extend the use of online meetings and it was not for the courts to set that legislation.
Chairman of the Local Government Association James Jamieson said the ruling was "very disappointing".
"Councils, by law, have to hold annual meetings within 21 days following local elections so many will now have to use very large external venues to allow all members of the council to meet in person," he said.
"Councils want to continue to have powers to hold online and hybrid meetings even when restrictions have been lifted."