Washington DC - An anonymous Canadian man is suing the US Department of Homeland Security over what he contends was an attempt to target him over social media posts critical of President Donald Trump.

The lawsuit was filed by the American Civil Liberties Union on Monday against Homeland Security Markwayne Mullin, contending that the DHS is attempting to "chill speech the government doesn't like."

According to the filing, the DHS reportedly sought "vast swaths" of information about the plaintiff's personal life over social media posts that criticized the Trump administration.

The legal complaint said that the anonymous Canadian – referred to only as John Doe – regularly posts political content under an online pseudonym.

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In February, the email account linked to his profile on X was subpoenaed by the DHS, compelling the release of personal, identifying information.

This is reportedly one of many such attempts by the department.

The incident occurred amid the crackdown by DHS agencies Immigration and Customs Enforcement and Customs and Border Protection in Minnesota.

Doe had been critical of the crackdown, criticizing the Trump administration's use of masked agents to round up and deport migrants en masse.

"I have long admired the United States for its commitment to free speech," the man said in a statement released by the ACLU.

"Never in a million years did I think that, after criticizing the US government, I would be targeted with a summons seeking to find out who I am, where I live, where I go and what I read online."

In a statement to CBC, a Google spokesperson clarified the process it undertakes when it receives a subpoena, explaining that its review process "is designed to protect user privacy while meeting our legal obligations."