Former FBI agent Mike German, now at the Brennan Center for Justice, explains how the US government's domestic surveillance and intelligence gathering operations are increasingly militarized. This is happening in three ways, German writes:

First, military agencies are conducting domestic intelligence collection against Americans, and providing that information to law enforcement officials. The National Security Agency scoops up domestic telephone calling data, as well as the content of U.S. international communications (“inadvertently” grabbing tens of thousands of purely domestic calls each year in the process). The FBI has direct access to this material, and can use it for general criminal purposes through so-called “back door searches.”

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Second, military agencies and personnel participate in formal and informal information sharing programs on the federal and state level, including between FBI Joint Terrorism Task Forces, state and local law enforcement intelligence fusion centers, and information sharing networks like the Navy’s Law Enforcement Information Exchange (LInX), and the FBI’s eGuardian program.

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Third, military intelligence tactics and attitudes rub off on law enforcement personnel assigned to intelligence matters. Most nations outlaw espionage, so foreign intelligence activities have to be carried out through stealth and deception. Avoidance of the law and contempt for the truth can become habitual among intelligence officials, but they simply have no place in a democratic government’s interactions with its own citizens.

Espionage and policing are totally different enterprises. The former is principally about political and economic power, while the latter is ostensibly about public safety. German shows that the bleeding of espionage tactics and mentality into the domestic policing context doesn't only imperil civil liberties. It also hurts public safety.