Bridges faced four major trials over a twenty year period. The first phase lasted from 1934 to 1940 under the auspices of the Immigration and Naturalization Service (INS), then part of the Department of Labor. The second phase of legal activity was from 1940-1945, after the INS was put under the jurisdiction of the Department of Justice. The third phase, 1948-1955, consisted of two trials, one criminal and one civil, in which the government attempted to denaturalize Bridges.

1934-1939: In 1934, two weeks after the San Francisco longshore strike began, the White House received complaints about Bridges as "a professional labor agitator from Australia." The INS was ordered to secure a field report on Bridges from the San Francisco office. The first INS investigations produced no basis for action against Bridges, but demands for Bridges' deportation continued to flow into the INS and the Department of Labor, resulting in an INS hearing in 1939.

Landis Hearing, 1939-1940: Frances Perkins, Secretary of the Department of Labor, selected James M. Landis, Dean of the Harvard Law School, to preside over the hearing. Dean Landis opened the hearing on July 10, 1939, on Angel Island, San Francisco headquarters for the INS. The proceeding, covering forty-five days of testimony, lasted until September 14. Landis submitted a report to Secretary Perkins in December, which found in favor of Bridges. Perkins approved Landis's report and dismissed the proceedings on January 8, 1940. The reaction to the Landis report was unfavorable. On June 13, 1940, the House of Representatives passed the Alien Bill, specifically calling for Bridges' deportation. In the Senate, a section was added to the then pending Alien Registration Bill (eventually to be known as the Smith Act) that made it unlawful for a resident alien at any time to belong to a group advocating the violent overthrow of the government. At the same time, Congress transferred the INS to the Justice Department.

Sears Hearing and Appeals, 1941-1945: In 1941, the Justice Department began a new hearing in San Francisco under Judge Charles Sears, a retired judge of the New York Court of Appeals. After hearing forty-four days of testimony between March 31 and June 12, Sears ruled that Bridges was deportable on the grounds that his cooperation with Communist-front groups and his sympathetic attitude toward Communist-sponsored programs and policies formed a consistent pattern of affiliation with the Communist Party. However, Justice Department procedures provided for a review of Sears' ruling by the Board of Immigration Appeals. This board overruled Sears' judgment and unanimously recommended in January 1942 that the warrant for Bridges' deportation be canceled.

In May 1942, Attorney General Francis Biddle, disagreeing with the Board of Immigration, issued a deportation order. Bridges immediately appealed the deportation order to the courts. The Circuit Court of Appeals denied Bridges' appeal late in June 1944, but a year later, the Supreme Court overruled Biddle and found in favor of Bridges.

The Supreme Court decision cleared the way for Bridges to secure citizenship. On August 8, 1945, Bridges was naturalized as a US citizen, with J.R. Robertson and Henry Schmidt as witnesses. During these proceedings, Bridges formally denied belonging to the Communist Party. Robertson and Schmidt supported his application by vouching for his good character.

Criminal Conspiracy Case, 1948-1955: As a citizen, Harry Bridges was as controversial as ever. His public opposition to the Truman Doctrine and the Marshall Plan, his support for Henry Wallace in the 1948 presidential election, and his later criticism of the Korean War made him suspect as a Communist sympathizer. In 1948, the INS launched an investigation to determine whether there was any possibility of revoking Bridges' citizenship. In 1949, the government charged that Bridges had perjured himself at his naturalization hearing, and that his union friends had knowingly lied when they had vouched for him. A grand jury indicted Bridges, Robertson, and Schmidt for perjury and for having engaged in a criminal conspiracy to secure Harry Bridges' naturalization fraudulently. The defendants sought a dismissal of the charges on several grounds. Two key government witnesses were Mervyn Rathborne and John Shomaker, former intimates of Bridges in union affairs in the 1930s. Both claimed to have belonged to the Communist Party. As the investigation continued, Bridges' attorneys raised the question of whether the three-year statute of limitations applied to this case. A trial lasting from November 1949 to April 1950 found the defendants guilty of both fraud and conspiracy. Bridges received concurrent sentences of two and five years; Robertson and Schmidt were also convicted.

On the same day in May 1949 that the grand jury had returned a criminal indictment against Bridges, the government filed a civil suit to cancel his naturalization on the ground that it had been fraudulently secured. However, all civil proceedings were stayed pending the result of the criminal trial. Following Bridges' conviction in April, on June 20, 1950, Judge George Harris, who presided at the jury trial, voided Bridges' naturalization papers based on the criminal conviction. On August 5, 1950, after Bridges spoke out at a union meeting to urge an end to the Korean War, Judge Harris revoked Bridges' bail and ordered Bridges jailed immediately. However, bail was restored after Bridges spent 21 days in jail. The Court of Appeals heard Bridges' trial appeal and unanimously upheld the conviction in September 1952. In 1953, the Supreme Court overruled both decisions on the grounds that the statute of limitations prevented the government from instituting criminal proceedings against Bridges for his alleged fraud in acquiring citizenship. At the same time, the Court restored Bridges' citizenship.

Civil Conspiracy Case, 1955: The civil proceedings, stayed by Judge Harris while the criminal case was going on, were once again put forward. When the Supreme Court reversed the conviction in 1953, it also handed down a separate ruling reversing the order on denaturalization. But within a month the general council for the INS was ready with a report recommending that the civil case be reactivated and brought to trial. The trial in San Francisco before Judge Louis Goodman lasted from June 20 to July 22, 1955. The government's civil action largely followed the pattern of the 1949 criminal trial. However, this time Goodman found in favor of Bridges by concluding that the government had failed to prove its case.