In the Brezhnev's era, i.e. the period when he held the office of General Secretary of the CPSU (1964-1982) the process of smuggling both by individuals and organised groups was already well-known, so it is hardly possible that it was anything new to Brezhnev. It is possible that you're referring to the process started in 1960 (so, in the late Khrushchev's era) that ended with the death penalty for the three main perpetrators: Ian Rokotov, Vladislav Faybishenvo and Dimitri Yakovlev who were initially sentenced to 8 years of prison for smuggling, selling contraband (including denim trousers), possession of foreign currency and illegal financial operations. In the following year, Khrushchev, during the official state visit in East Berlin learned first-handedly that Moscow is commonly considered the largest hub of black market operations within the Warsaw Pact and thus decided to bolster his position by the campaign undertaken against smugglers and black marketeers. During the session of the Central Committee of CPSU he presented a letter allegedly written by the workers of the Leningrad Steel Mill who were outraged by the 'lenient treatment of parasitic social element' (historians argue about veracity of this claim, and the letter is generally considered to be Khrushchev's fabrication). This led to the re-trial, where the punishment was increased from 8 to 15 years of prison. Shortly after, on 1st July 1961, under the Khrushchev's pressure, Presidium of the Supreme Soviet quickly proclaimed the act of 'Increase of severity of the criminal punishment for the violation of the financial operations' allowing the use of death penalty for the financial crimes. After second re-trial, all Rokotov, Faybishenko and Yakovlev were sentenced to death. As the verdict was openly violating the 'lex retro non agit' rule, even several of the lawyers taking part in the process to voice their opposition but the political pressure ensured the execution of the verdict.

Death penalties for criminal financial operations (including smuggling) were very in the Soviet Union (as seen above, they weren't even considered by the Penal Code until 1961), but they existed, although they were usually reserved for either significant breaches of law, linked to illicit currency or gold trade (Soviet citizen were forbidden from possessing foreign currency) or abuse of power in order to conduct such crimes, i.e. corruption. It is safe to say that no one was sentenced to death for smuggling or selling smuggled jeans alone.