Illinois Attorney General Lisa Madigan has joined dozens of peers in asking major wireless phone carriers to adopt technology that allows users to block unwanted calls.

The Democrat's signature appears on a letter released Wednesday from the National Association of Attorneys General to the heads of five cellphone-service providers.

It says the Federal Communications Commission declared last month that call-blocking services requested by customers would not violate federal law and asks the companies to develop them.

The letter went to executives at AT&T, Sprint Corp., Verizon Communications, T-Mobile USA and Century Link Inc.

Industry officials told a U.S. Senate committee in July 2013 that "legal barriers" prevented call-blocking services.

That prompted 39 attorneys general to request a ruling by the FCC, which issued an opinion June 18.

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