Ritter told reporters outside of his New York home that the raid was related to a suspected violation of the Foreign Agents Registration Act (FARA), a law that requires individuals or entities engaging in lobbying or other activity on behalf of a foreign country to register as foreign agents with the US Department of Justice.

"The search warrant is related to concerns apparently the US government has about violations of the Foreign Agents Registration Act. I will tell you right now I am not in violation of the Foreign Agents Registration Act … and hopefully, by executing the search warrant and taking the information that they did, they will rapidly reach that conclusion," Ritter said.

FARA has been used to target people for their political views and is selectively enforced. For example, the pro-Israel lobbying group AIPAC, which spends millions on pro-Israel candidates and openly boasts about swaying US elections, is not registered as a foreign agent.

Ritter, a former US Marines Corps intelligence officer, said there was "no doubt" he was being targeted for his political views and said the raid would have a "chilling effect on free speech." He said the warrant allowed the FBI agents to look for "electronic equipment" and said they were "clearly interested in communications that I had with people related to the work I do."

Ritter recently had his passport seized by Customs and Border Patrol officers when he was boarding a plane from New York to Istanbul while traveling to Russia for the St. Petersburg International Economic Forum. According to Ritter, the officers said they were seizing his passport on orders from the State Department.