SALEM, Ore. -- Oregon drivers caught smoking in cars with kids may face hefty fines under a new state law. Gov. John Kitzhaber signed into law on Tuesday a bill that prohibits drivers from lighting up if a person under 18 is also in the car.

The bill was the subject of a fiery debate in the Legislature. Supporters said secondhand smoke is a health hazard and children shouldn't be harmed by their parents' bad decision to smoke. Critics said the state shouldn't regulate what drivers do in their own cars.

A police officer could enforce the ban only if the driver had been pulled over for a separate traffic violation. A maximum fine for the first offense would be $250.  The law also covers marijuana and regulated narcotics.