Kremen, et al. v. United States was an ancillary case from the 1950s Smith Act prosecutions of the Communist Party. After being convicted under the Smith Act in 1951, four Communist Party leaders failed to surrender, and instead went underground. One of these men, Robert Thompson, was captured on August 27, 1953, in a cabin near Twaine Harte, in the Sierras of California. Arrested along with Thompson were five other Party members who were subsequently charged with harboring a fugitive. This became known as the harboring case.

The five defendants in this case were Shirley Kieth Kremen (also referred to as Lee Kaplan), and at 21 years old, the youngest Party member to be prosecuted during this period; Sidney Steinberg (also referred to as Sidney Stein or Joshua Newberg), a former Assistant National Labor Secretary of the Party who had successfully evaded arrest since 1951 when he was indicted under the Smith Act; Carl Ross (also referred to as Carl Rasi or Robert Newman), a former State Secretary of the Minnesota Communist Party; Samuel Coleman (also referred to as William Gordon), a Party leader from New York; and Patricia Blau (also referred to as Janet Conroy), from Denver, Colorado. Norman Leonard and Richard Gladstein were both involved in their defense. First convicted on April 26, 1954, in 1956 the 9th Circuit Court of Appeals upheld the guilty verdict. The Supreme Court, however, reversed the decision in 1957 on the grounds that the seizure of evidence used against the defendants had violated the Fourth Amendment.

When the F.B.I. originally arrested the group, it confiscated the entire contents of the cabin where the defendants had been staying. As can be seen in the Government Exhibits folders and in the inventory of seized property, this included everything from Greig records to "1 pair socks--men's--dirty." Leonard and Gladstein requested an accounting from the F.B.I., and received an 18 page inventory (see folder #2/24). It its decision, the Supreme Court said that it could not condone the law enforcement agency's indiscriminate search and seizure. The timing of the case is important. By 1957 the legal climate had changed and the U.S. government was losing its efforts to convict Communist Party members. In this case, the Supreme Court rebuked the F.B.I. for its overzealousness.