Several years ago, I had lunch with a US government official who told me about a trip that I had taken, that almost nobody knew about. I didn't have to ask him where he got the information. For as long as I can remember, our government has been spying on dissidents, especially those who oppose crimes committed in the name of "national security".

When I was a student at the University of Michigan, the FBI took down the license plates numbers of the people who drove to our meetings of the local Latin American Solidarity Committee, which was trying to end the US-sponsored terrorism and wars in Central America. This we learned from documents released under the Freedom of Information Act. The surveillance of our local, peaceful, and law-abiding group – long before the Patriot Act or the "war on terror" – was so extensive that one of our members who wrote a history of the group had to thank the FBI for keeping such a complete and detailed record of our activities.

The current revelations of a vast, secret NSA surveillance program are, of course, a continuation of what our government has been doing for the past century – the main difference being that the dragnet has gotten much larger due to change in communications technology. But there is an often-overlooked political reason for this mass intrusion on our personal communications: the government is gathering actionable intelligence in order to use it against those who oppose unpopular, unjust, and often criminal policies of that same government. And it has good reason to do so, because that opposition can be quite effective.

It is well-known that a mass protest movement, as well as its lobbying of Congres,s helped get us out of Vietnam. It is less widely known that the movement against the Central American wars in the 1980s, which involved hundreds of thousands of people, succeeded in cutting off congressional funding for the war against Nicaragua. And perhaps more historically significant, that result caused major problems for then-President Reagan, when his government turned to illegal funding and got caught, resulting in the infamous "Iran-Contra" scandal.

More recently, mass education and mobilization played a significant role in getting us out of Iraq. "With Election Driven by Iraq, Voters Want New Approach" was the headline in the New York Times just before the November 2006 congressional elections; it seems clear that the Republicans lost the House of Representatives that year because of opposition to that unpopular and illegal war. (Not coincidentally, that was the only year that the US TV media showed many images of terrible violence in Iraq – demonstrating, once again, that these wars are more likely to be politically viable when their gruesome reality can be kept hidden from the public.)

Now to the present: two ongoing crimes that the Obama administration has been forced to address because of domestic opposition are the drone strikes that have killed hundreds of civilians in Pakistan, Yemen and other countries; and the illegal and brutal detention of prisoners at Guantánamo. The drone strikes are particularly outrageous for a number of reasons. There are "signature strikes", in which the US government doesn't even know exactly whom it is killing, but bombs people that it thinks might have some association with terrorism. Then, there are the "double-tap" strikes where – in a move similar to the double-blasts of terrorist bombers in Iraq – the drones hit their target and then bomb the first responders who come to help the wounded. And there is growing evidence that the drone strikes have terrorized civilians and made more people in the target areas want to kill Americans – not surprisingly.

The drone strikes were supposed to be "secret" and have only recently been publicly acknowledged by the Obama administration. Growing opposition led to Senate hearings in April, and finally President Obama, in his 23 May speech at National Defense University, had to pledge that "before any strike is taken, there must be near-certainty that no civilians will be killed or injured." If he is held to this pledge – a big "if", at present – it would eliminate "signature strikes" and almost all drone strikes. While these crimes have not yet been stopped, the pressure to end the worst abuses is building.

President Obama was also forced to address the issue of Guantánamo in his speech, saying that Guantánamo has "become a symbol around the world for an America that flouts the rule of law …holding people who have been charged with no crime on a piece of land that is not part of our country. Look at the current situation, where we are force-feeding detainees who are being held on a hunger strike … Is this who we are?" More than half of the 166 prisoners there have been cleared for release, yet they are still being held; 56 of those are from Yemen.

Medea Benjamin brought these issues to millions of people when she interrupted President Obama in his speech, demanding an end to the drone killings, the release of the Guantánamo prisoners, and an end to the war in Afghanistan.

Benjamin is the co-founder of Code Pink, a very effective grassroots antiwar group that has become the conscience of the nation as our leaders have drifted into a state of permanent warfare. They and their allies are living proof that committed groups of active citizens can actually force the most powerful government in the world to change course.

This week, Code Pink led a delegation to Yemen, visiting families who have members at Guantánamo and families who have lost relatives to US drone strikes, seeking to raise the profile in American public opinion of these families' stories of unjust suffering at the hands of US foreign policy. It is an effort worthy of attention; you can be sure that the government is giving its every move special and personal attention.

Since the United States government presides not just over its own residents, but also, to varying degrees, over a vast worldwide empire, it has special problems in controlling its citizenry. It is not like other governments – both democratic and non-democratic – that are only concerned with keeping the ruling party in power. Rather, much of its unconstitutional activities are directed at those who – for moral, political, or other reasons – don't like being part of an empire, or the human costs and loss of civil liberties associated with it.

This is a large number of Americans, usually a majority. Hence the perceived need for increasing surveillance, secrecy and punishment for those who expose these things.