JEFFERSON CITY - A law banning texting for Missouri drivers under the age of 21 took effect Friday as some law enforcement and state government officials questioned the enforceability of the restriction.

The law, passed by the Missouri legislature earlier this year as part of an omnibus crime bill, will enable law enforcement officials to stop young drivers suspected of texting at the wheel.

Rep. Scott Lipke, R-Jackson, sponsor of the House bill that included the provision to ban teens from texting, is worried the new law will be difficult to enforce.

"If you're a law enforcement officer sitting on the side of the road and you see somebody come by and they've got their hands on their phone, how does that officer know whether or not you're dialing a phone number or texting?" Lipke said.

Being able to spot illegal texting from afar is not the only challenge facing law enforcement officials. Patrol officers will also need to identify drivers who may be texting as being under the age of 21.

Lt. John Hotz of the Missouri State Highway Patrol said the decision to pull over a driver for texting will be one based largely on appearances.

"If we see someone who appears to be texting on their device and they appear to be under the age of 21, then they can be stopped," Hotz said.

As the law is written, texting while driving is classified as a primary offense, meaning drivers can be stopped by law enforcement officers under suspicion of texting alone. Hotz, however, said that only those motorists driving dangerously would likely be pulled over and that safer drivers, even those engaged in text messaging, could be overlooked by law enforcement.

Under the new law, a ticket will cost up to $200 for those drivers who are caught texting on the road. Hotz believes making texting illegal while driving will prevent accidents, but Major Tom Reddin of the Boone County Sheriff's Department remains unconvinced the law will act as an effective deterrent.

"Honestly, I think this law is going to get violated right and left," said Reddin.

The new law will apply only to those drivers between the ages of 16 and 21. In 2007, this age group experienced more crashes than any other, according to the Missouri Department of Transportation.

Reddin and Lipke suggest expanding the illegality of texting to include drivers of all ages, not just those within the highest-risk age group. Said Lipke, "Anyone that texts and drives is putting themselves and others at risk."

Originally, a universal ban on texting while driving was proposed by state Sen. Ryan McKenna, D-Jefferson County, who could not be reached for comment. McKenna, Lipke said, still hopes to expand the law. Lipke expects such a provision could be proposed once the next legislative session begins and the new law has been in place for a few months.