Players at the World Cup could face a red card if they cover their mouths when speaking to opponents during confrontations.
The decision was taken during a special meeting of the Fifa Council in Vancouver, Canada, on Tuesday, where two Fifa-proposed law amendments were approved.
Players who leave the pitch in protest at a referee’s decisions could also now face a red card, following ugly scenes at the Africa Cup of Nations final between Morocco and Senegal.
Both law changes have been approved as competition opt-ins by the International Football Association Board (Ifab).
Fifa has confirmed they will be adopted at this summer’s World Cup.
The issue of players covering their mouths became high profile in February when Benfica winger Gianluca Prestianni raised his shirt while speaking to Real Madrid’s Vinicius Jr during a Champions League game.
The Argentina international was accused of racist abuse and provisionally banned for one match. Following a Uefa investigation, Prestianni was found guilty of homophobic conduct and banned for six matches – three of which were suspended.
The issue was discussed at the Ifab annual general meeting in Wales later that month where it was agreed the matter would be on the agenda at the Fifa Council.
The decision remains at the absolute discretion of the referee, who will consider all circumstances before issuing a red card.