Strzok was part of special counsel Robert Mueller's investigation but was removed from Mueller's team after the text messages surfaced.
Goelman said that his client's firing was politically motivated and that his texts represented political speech protected by the First Amendment.
Peter Strzok was sacked on Friday after serving in the Federal Bureau of Investigation for 21 years, his lawyer Aitan Goelman said in a statement.
Special counsel Robert Mueller fired Strzok from the Russian Federation investigation after it was discovered that Strzok had been sending texts to a fellow FBI agent bashing then-candidate Donald Trump and saying that Trump would never become president because "we'll stop it", while he was working on the Clinton email investigation during the 2016 election.
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Strzok's attorneys called his dismissal "not only a departure from typical bureau practice", but a decision that contradicted earlier commitments by FBI Director Christopher Wray to follow standard process in dealing with its personnel matters.
During the 2016, Strzok would regularly text with attorney Lisa Page expressing his distaste for Trump. And in another, they referred to a backup plan they could deploy if he were elected.
In a second tweet today, Trump wrote, "Just fired Agent Strzok, formerly of the FBI, was in charge of the Crooked Hillary Clinton sham investigation". But he told Congress the bias was "completely antithetical to the core values of the department and extremely serious". Trump tweeted. "The list of bad players in the FBI & DOJ gets longer & longer". In June, his conduct was laid out in a wide-ranging inspector general's report on how the FBI handled the investigation of Clinton's emails in the run up to the 2016 election. "When I won it became a big deal and the Rigged Witch Hunt headed by Strzok!" In the twilight of his career, Strzok was integral to two of the bureau's most high-profile investigations: the Russian Federation case, and the investigation into Hillary Clinton's use of a private email server while secretary of state. Goelman said the move undercuts the FBI's repeated assurances that Strzok would be afforded the normal disciplinary process. "It was a total fraud on the American public and should be properly redone!"
Former FBI lawyer Lisa Page arrives for a House committee deposition, one day after the session involving Strzok.