Vincenzo Nibali (Bahrain-Merida), Fabio Aru (Astana) and defending champion Giacomo Nizzolo (Trek-Segafredo) have been reminded that they must ride this month's Italian National Championships.
The Italian Cycling Federation ruled during the winter that from this year all professional riders must race the national road race.
If a rider fails to do so and can't provide a reasonable reason why - such as injury - it means that they risk not being selected to represent the country during the rest of the season in races such as the World Championships.
Davide Cassani, the country's national coach, told La Gazzette dello Sport that both France and Belgium have a similar rule and that riders should place the nationals high on their list of priorities to win.
>>> WorldTour transfer rumours: Who could be switching teams for 2018?
"The Italian championship is an important race and so we wanted to send a clear signal," he said.
“We want that the riders feel obliged to take part so that we can protect Italian cycling. Certain values have to be respected and the Italian Azzurra jersey has to be honoured.
"Whoever doesn’t take part in the championship without a valid reason, will not be selected for the European and World Championships."
This year's race, at 245km long for the men, is being held in the Piedmont region of Italy, not so far from Turin, on June 25.
Nizzolo won the 2016 edition and Nibali won the two nationals in the two years previous. Canyon-SRAM rider Elena Cecchini has won the women's title for the past two years.
Britain's national road race takes place in the Isle of Man on the same day. The men's race features two ascents of Snaefell mountain, while the women complete one.
Mark Cavendish (Dimension Data) is on the start list to race in his home island. Lizzie Deignan (Boels-Dolmans) is the women's favourite.
