Opposition leader Boris Nemtsov gives a television interview in 2011. (Alexander Zemlianichenko/Associated Press)

THE RULE of law means, at its most fundamental level, that no one is above the law. The end of a trial in Moscow of five men accused of taking part in the murder of opposition leader Boris Nemtsov shows quite clearly that that rule does not apply in Russia. The five Chechen men were convicted of carrying out the assassination, but the people who ordered the killing were not pursued and not found.

Nemtsov, then 55, was gunned down from behind as he crossed a bridge near the Kremlin Walls on Feb. 27, 2015. He had once been a rising young reformer as governor of the Nizhny Novgorod region in the early days after the Soviet collapse, and later in the 1990s served as a deputy prime minister under President Boris Yeltsin, attracting speculation as a possible Yeltsin successor. By the third term of President Vladimir Putin, Nemtsov had become a nettlesome critic of the president, preparing reports calling out corruption among Mr. Putin’s cronies. Before his death, he had spoken out publicly against “Vladimir Putin’s war,” the instigation of an armed uprising in southeastern Ukraine.

The brazen, coldblooded murder was shocking. Many friends and family have asked how Nemtsov could have been assassinated so close to the Kremlin without some kind of official connivance. The court was not so curious. After an eight-month jury trial, the five Chechens were convicted, including Zaur Dadayev, who was identified as the triggerman. The other four served as accomplices, the court found, and the group was promised 15 million rubles, or about $254,000, for the attack. The court did not pursue who may have ordered the hit.

Nemtsov’s family has demanded that investigators examine the role of Ramzan Kadyrov, the Chechen strongman, but he was not questioned. Testimony at the trial showed that a Chechen police commander who has since disappeared permitted Dadayev to go to Moscow and provided an apartment there. The commander’s driver was the one who offered the payment to the killers — he has also fled.

Such contract killings with impunity have been a terrible black mark on Russia for more than two decades. On Oct. 7, 2006, the courageous journalist Anna Politkovskaya was shot to death in her apartment building. The men who killed her were caught and convicted, but the person who ordered it was never found. The list of such murders runs long: Journalists, politicians and businessmen have been the most common targets.

The sad fact is that Yeltsin failed to build a state based on rule of law, and Mr. Putin did not seriously try. Though a Russian judicial system exists and post-Soviet laws are on the books, enforcement can at times be arbitrary in the extreme, and the powerful enjoy an exalted position, beyond reproach and beyond questioning.