The nationís largest theatre owners announced Tuesday that they would seek to require young moviegoers to show photo identification at R-rated films. The procedure would be similar to proof-of-age checks for alcohol and tobacco sales. The policy would be a voluntary enforcement procedure to attempt to keep children and teenagers from seeing movies in theatres restricted to viewers 17 and older.The guidelines were unveiled by the National Association of Theatre Owners (NATO), a North Hollywood-based group that represents about two-thirds or 20,000 of motion picture screens in the country, from large chains to independents. With President Clinton along side, William Kartozian, NATOís President said at the White House reception, ""We as theatre owners feel our responsibilities as keenly as does anybody. Young people had best be ready to show their ID.""""From now on parents will know that the R-rating means what it is supposed to mean: Restricted, no one under 17 without a parent or guardian, and no exceptions,"" said President Clinton. ""When you drop them off, you shouldnít have to worry about your G-rated kids getting into R-rated movies.""The announcement by the theatre owners is a reaction to tougher measures being debated in Washington to force Hollywood to curb its most violent movies and their availability to children.The existing rating code was co-sponsored and adopted in 1968 by the Motion Picture Association of America and NATO. The system operates with a board that rates movies based on theme, violence, language, nudity, sensuality and portrayal of drug use. Films are rated in the following categories: G for general audiences (no strong words, nudity or sex scenes), PG for parental guidance, PG-13 for stronger parental guidance, R for restricted (children under 17 must be accompanied by an adult) and NC-17 for no children under 17 can be admitted.The White House said that it would continue working on getting the cooperation of the 35 percent of theatre owners not represented by NATO.But critics see no real practical means to regulate or police admissions in sprawling multiplexes where children frequent movies, skittering from one movie door to another. And with teenagers serving as the primary moviegoing audience there is little financial incentive to lose that lucrative income stream. Thus, realistically this announced policy is first and foremost a response to the Presidentís moral call to arms, a challenged first heard on a May 15 radio address to voluntarily enforce the 31 year-old rating code.