Sidney Leonard Jaffe (22 December 1924 – 16 July 2005) was an American-born Canadian businessman who was kidnapped from outside his Toronto home in 1981 by American bounty hunters Timm Johnsen and Daniel Kear and transported to Florida after failing to appear for a trial there on charges of land sales fraud. His conviction on the fraud charges was overturned on appeal; his conviction on an additional charge of failure to appear for trial was upheld, but he was paroled after two years and returned to Canada. At the request of the Canadian government, Jaffe declined to appear at a new Florida trial on further land fraud charges in 1985. Johnsen and Kear were extradited to Canada and convicted of kidnapping in 1986, but were set free pending appeal, and their sentences were reduced to time served in 1989, after which they returned to the United States. The Jaffe incident caused significant tensions in Canada–United States relations, and resulted in a 1988 exchange of letters between the two countries on cross-border kidnappings.

Sidney Leonard Jaffe was born in Manhattan on 22 December 1924. A native of New York, and moved to Canada in the early 1970s. In Canada, he worked as an international economist. After his move, he also continued to do business in the United States. He was involved in land deals in Putnam County, Florida as an employee of the Atlantic Commercial Development Corporation. Jaffe sought purchasers for subdivided lots of land, but due to a dispute with the original holder of the mortgage on the lots, Jaffe issued quitclaim deeds rather than warranty deeds to purchasers. In August 1980, Jaffe was arrested on twenty-eight counts of violating the Florida Land Sales Practices Act. Accredited Surety & Casualty posted a US$137,500 bail bond for him. Jaffe then returned to Canada and applied to naturalise as a Canadian citizen. He failed to appear at his May 1981 trial, and was tried in absentia.

AS&C faced forfeiture of its bail bond if Jaffe were not returned in 90 days. As a result, AS&C employee Daniel Kear, along with independent bounty hunter Timm Johnsen, then traveled to Canada in pursuit of Jaffe. In September 1981, they intercepted Jaffe at his apartment building as he returned from jogging, and took him in their car back to the United States. Jaffe later testified that Johnsen and Kear threatened him to obtain his cooperation, telling him that his daughter would be harmed if he did not cooperate and that they could return him to Florida "dead or alive", while attorneys for Johnsen and Kear claimed that Jaffe cooperated willingly because of the bail bond agreement.

In November 1981, Jaffe was convicted on the land fraud counts and an additional count of failure to appear for trial.

This assertion of jurisdiction by the Florida court over Jaffe despite his illegal kidnapping from a foreign state was an example of the controversial legal doctrine of male captus bene detentus. In U.S. law, this doctrine goes back to the 1886 Supreme Court case Ker v. Illinois, in which Ker was accused of embezzling funds from a Chicago bank and fled to Lima, Peru. Extradition papers had been drawn up, but it was difficult to actually effect extradition due to the Chilean occupation of the city in the ongoing War of the Pacific, and so two detectives simply abducted Ker and brought him to Illinois. The Supreme Court ruled that the kidnapping had not violated Ker's right to due process as long as he had been properly indicted and tried. At the time of Jaffe's kidnapping, the U.S. recognized only limited exceptions to the general rule in Ker; specifically, in the 1932 case Cook v. United States, the Supreme Court had ruled that where a treaty provision sets explicit territorial limits to jurisdiction, seizure or arrest in violation of that provision meant that a court could not exercise jurisdiction over the defendant so seized or arrested. In that case, the U.S. Coast Guard had seized a British vessel at sea for liquor smuggling 11.5 miles (18.5 km) off the coast of Massachusetts, beyond the "one-hour sailing limit" within which the Coast Guard could legally seize the vessel under the relevant 1924 U.K.–U.S. treaty, and the court ordered that the vessel be released to its owners. However, as Kathryn Selleck of Boston College Law School observed, the U.S.' extradition treaty with Canada did not explicitly state that the U.S. had no jurisdiction in Canadian territory, and so Jaffe would not be able to avail himself of the Cook exception as a defence.

Johnsen and Kear's actions provoked international outrage, pitting Canada's sovereignty against Florida's desire to punish what it believed was fraud. As an August 1982 editorial in The Montreal Gazette put it, "no matter how it turns out, justice may be served only at the cost of an injustice".

In September 1983, the Florida Fifth District Court of Appeal overturned Jaffe's conviction on the land fraud charges on the two grounds that the prosecutors had made paperwork errors and that the judge below had misdirected the jury. However, by that time State Attorney Stephen Boyles had already filed a new organized fraud charge. In August 1983, Jaffe's lawyer Daniel Dearing filed a motion in state court to dismiss the new fraud charges, stating that they were "filed in bad faith without probable cause in order to hold the defendant and frustrate his release on parole or upon bond during pendency of his appeal". Similarly, Jaffe stated to the Orlando Sentinel that Boyles had only filed the new charges because he feared Jaffe would win his appeal. Dearing's motion argued that the evidence on which the new charges were based was already known at the time of Jaffe's 1982 trial, and if it had been included in the original charges the defence would have moved for consolidation of charges. Jaffe had served nineteen months of his sentence on the charge of failure to appear for trial, and would soon be paroled, as Putnam County continued to hold Jaffe pending determination of bail on the fraud charges.

In October 1983, Judge Edwin Sanders of the Seventh Judicial Circuit Court of Florida approved a US$150,000 bond for Jaffe on the new fraud charge. Rather than a bail bondsman, the bail bond was backed by a letter of credit from the Florida State Bank in Tallahassee; Boyles stated, "It is unusual for a bank to become a surety. I wouldn't think they would do that unless they had some sort of proof that it was salted away, so to speak". Soon after his release from Avon Park Correctional Institution, Jaffe returned to Toronto and was reunited with his wife and daughter. However, the following month, Sanders declined to dismiss the new fraud charge. Jaffe did not return to Florida for an October 1984 bankruptcy hearing, at which a judge granted a motion by attorney Terrance Schmidt that Jaffe be ordered to repay $41,570 he had allegedly taken from the accounts of his corporation. He was found in contempt of court, and after his failure to attend a sentencing hearing two weeks later, Florida Seventh Circuit Judge E. L. Eastmoore sentenced him in absentia to 180 days in prison.