Prosecutors said in a statement that after a lengthy review, there was insufficient evidence to prove any officer violated the law when using force, although some might have used 'questionable tactics.' They described the incident as 'unfortunate and preventable' but said that the office was 'closing our file and will take no further action in this matter.' Last year, Police Chief William J. Bratton said he planned to discipline 11 officers and called for the termination of four others for their roles in the melee in which police were accused of using excessive force to clear immigration rights demonstrators and journalists. LAPD officers were videotaped wielding batons and shooting rubber bullets in an attempt to disperse a largely peaceful crowd. A scathing internal investigation into the incident blamed poor leadership and overly aggressive tactics by officers in the field. Earlier this year, the Los Angeles City Council agreed to pay nearly $13 million to people injured or mistreated in the melee. Under the settlement, the department must submit to court oversight of its crowd-control procedures -- another layer of federal involvement that comes as LAPD leaders are impatient to be free of a long-standing and more onerous monitoring program imposed after the Rampart Division corruption scandal. Prosecutors reviewed an extensive LAPD investigation into 30 officers that included 7,500 pages of documents. 