I am a Pakistani lawyer who is suing the CIA for killing innocent civilians through drone strikes in my home country. This month, the US state department prevented me from travelling to the United States to participate in a conference hosted by the human rights programme at Columbia University law school in New York City.

I have been granted US visas before and no reason was given by the state department for refusal on this occasion: despite repeated enquiries, we were merely told there was a "problem" with my application. If seeking justice through the law – instead of violence – is the reason for banning my travel, then mine is another story of how government measures in the name of "national security" have gone too far.

Although I have previously held consultancies with USAID, and helped the FBI investigate a terrorism case involving a Pakistani diplomat, my relationship with the US government changed dramatically in 2010, when I decided to take on the case of Karim Khan. Karim Khan was away from home on New Year's Eve 2009 when two missiles fired from what we believe was a CIA-operated drone struck his family home in North Waziristan and killed his son, aged 18, and his brother, aged 35. Informed over the phone of their deaths, he rushed back to find his home destroyed and his brother's family – now a widow and two-year-old son – devastated.

Khan believes his son and brother were innocent victims. His brother, who had taken the surname Iqbal in honour of the famous Pakistani poet, was a schoolteacher who had returned to their ancestral village, shortly after finishing his master's degree in English literature, because he believed education was vital for his countrymen's improvement. Khan's teenage son helped out at another government school in the area.

To avenge their deaths, Khan could have joined the Taliban insurgency against the United States. Instead, he put his trust in the legal system. In November 2010, we initiated legal notices against the CIA and the US secretary of defence for their wrongful deaths. Since then, more than 35 families from Pakistan have come forward and joined us in our legal proceedings.

So, why would the US government want to prevent me from discussing these cases at Columbia law school? Perhaps, it is because our legal challenge disrupts the narrative of "precision strikes" against "high-value targets" as an unqualified success against terrorism, at minimal cost to civilian life.

As a lawyer in Pakistan, my experiences tell a different story. A 17-year-old boy named Sadaullah – another victim of the drone attacks – sought my help shortly after we filed Karim Khan's case. In September 2009, when he was 15 years old, Sadaullah was serving food at a family iftar, the traditional breaking of the daily fast during the holy month of Ramadan, when missiles from a drone struck his grandfather's home and killed four of his relatives. Falling debris knocked Sadaullah out, but he survived. When he awoke in a Peshawar hospital, he found that both his legs had been amputated and shrapnel had penetrated his eye, rendering it useless. Pakistani media reported that the strike had killed Ilyas Kashmiri, a militant leader. But months later, Ilyas Kahsmiri was seen alive in Afghanistan. It was only a few weeks ago that the militant was reportedly killed in yet another drone strike.

The New America Foundation, a US thinktank, estimates that the drone campaign has killed 35 high-value targets. But for every assassination, it seems a more ferocious and extremist leader has emerged. Thus, Pakistanis continue to be victims of terrorism. Suicide attacks are becoming more indiscriminate and claiming more lives – at least 6,302 have died since 2008, according to news reports.

This chaos within Pakistan makes Karim Khan's story all the more powerful as a rejection of retributive violence in favour of the rule of law. As they seek investigation, judgment and redress for any wrong done, my clients' impulses are a testament to how dearly people the world over – and not just in the west – value the principle of due process and the right to plead a cause.

Instead of preventing me from speaking with American colleagues about these legal cases, the US government should support our attempt at justice within the law – even if it disagrees with our view of the facts. Let us debate and sometimes disagree; after all, that is how American justice is supposed to be done.