The popular ride-sharing services Uber, Lyft and Sidecar each received letters from the district attorneys' offices in San Francisco and Los Angeles admonishing them to change their companies' operations, which are in violation of California State laws.

According to the letters, the services, which let passengers who are sharing the vehicle go the same route but pay separately, violate the public utility code that restricts services from charging multiple customers for the same ride.

They also want the literature in the marketing of the companies removed, which mislead customers into thinking the background checks they conduct on their drivers are more comprehensive than they truly are.

Conventional San Francisco taxi companies have also complained that Uber and Lyft don't have the proper paperwork to drop off and pick up passengers at the airport.

Uber says that the laws were written for limousines in an era before smartphones and that legislation needs to be updated as technology opens up new opportunities for commuters.

Similarly, Sidecar said that the ride-sharing or carpooling service it offers is more cost-efficient for many commuters and better for the environment.

"Shared rides are great for California because they are safe and affordable, cut down on traffic congestion and reduce pollution," the company said. It will also continue operations as normal.

If the new carpooling services offered by the companies are received well by passengers, they could potentially cut taxi driven miles by 40 percent.

The letters sent to the three companies include suggestions that they petition local lawmakers to update state code if they believe the current laws to be obsolete. But in the meantime the current laws need to be followed.

California is not the only place where ride-sharing app services have come under fire. In Europe, several taxi firms in Germany have called the services foul and said they violate local taxi rules and regulations for safety, insurance, and licensing.