Law enforcement where? The most common languages (after English) in the US are:
Spanish (30m+ people; 50+% in CA, TX, FL; NY, IL, AZ, NJ & CO have 1m+)
Chinese (3m; 40% in CA)
Tagalog (1.6m; mostly HI, CA, NV)
Vietnamese (1.5m; mostly CA, WA, OK, NE )
French (1.3m; 2m if you include Fr Creole; LA, ME, NH, VT)
Korean (1.2m; mostly GA & VA and LA, NYC, DC)
German (1.0m; midwest, esp ND)
Arabic (1m, 40% around Detroit)
Russian (>1m; mostly NY & CA)
Italian (>1m; mostly NY & NJ)
Also, Arabic is not a unitary language. MSA (Modern Standard Arabic), which is mostly what is taught in schools in the US is useful, but the 4 main dialects are pretty different when spoken (I know Libyans who say they struggle to understand Lebanese Arabic).