Senator Ed Markey (D-MA) has written a public letter to the Department of Justice seeking information about a phone surveillance program disclosed by the Wall Street Journal. Under the program, operated by the US Marshals service in coordination with federal and local law enforcement agencies nationwide, officials fly cell phone spying gear called "dirtboxes" in planes high above our homes, scooping up huge quantities of information about the whereabouts and possibly the communications of millions of people.

It's not the first time Senator Markey has used his office to shine sunlight on cell phone surveillance. In 2011 and 2013, Markey asked phone companies for records disclosing how many law enforcement requests for user information they receive each year, including the type of demand made on accounts. Thanks to his requests, we learned that millions of people are spied on during routine criminal investigations in the United States today, even if investigators never provided any evidence to a judge that the targets were involved in criminal activity.

Now Markey's going straight to the source of the demand for widespread cell phone surveillance: the government. Stay tuned for details Markey's letter produces about the dirtbox spy program.

Transparency must come before there can be meaningful government accountability. Kudos to Senator Markey for remaining a stalwart privacy defender in the senate and using his power to compel disclosures about troubling surveillance programs. We need this type of advocacy now more than ever.