Many of today's radar detectors also work in conjunction with smartphone apps. Not legal everywhere Beware that radar detectors are prohibited in Virginia and the District of Columbia, as well as on U.S. military bases. In Canada, they are prohibited in Manitoba, New Brunswick, Newfoundland and Labrador, the Northwest Territories, Nova Scotia, Nunavut, Ontario, Prince Edward Island and Quebec. In addition, 20 states besides Virginia and the District of Columbia prohibit the use of radar detectors in commercial vehicles. If you're ticketed for unlawful use of a radar detector as a non-commercial driver, you'll face a fine of up to $300 in the District of Columbia. In Virginia, you'll pay about $100. In Fairfax County, for instance, the fine is $40, and the processing fee is $62.
Source: http://www.foxbusiness.com/personal-finance/2014/02/18/radar-detectors-and-your-car-insurance/