The House of Representatives on Wednesday refused to allow cancer patients and other severely ill people to smoke marijuana to ease pain, as opponents argued the measure was a back-door attempt to legalize the substance. By a vote of 264-161, the House rejected a measure that would have stopped federal law enforcement authorities from prosecuting medical marijuana users in 10 states that allow it when prescribed by doctors.This marked the third time since 2003 that the House has defeated the initiative. This year, supporters picked up 13 votes.Proponents of the controversial legislation hope to build Republican support and could try for another House vote next year. Only 15 Republicans out of 231, supported the measure.