Voynov was charged with felony domestic violence two weeks ago. The Russian Olympian is barred from all team activities under the terms of his suspension, which began after his arrest Oct. 20.
Yet Voynov joined his teammates during their usual morning skate at the club's training complex Tuesday before the defending Stanley Cup champion Kings host the Boston Bruins. Voynov participated in a team workout for the first time since his suspension, lining up with injured fellow defenceman Alec Martinez.
Coach Darryl Sutter initially was vague about the reason Voynov practiced with the Kings, calling the workout an optional skate. The team, which had firmly supported the league's indefinite suspension of Voynov, clarified its position hours later.
"This was clearly a mistake on our part and we accept full responsibility," the Kings said in a statement. "It is incumbent upon us to be more vigilant in managing this situation to ensure that Slava's allowable training activities always remain separate from the team."
Voynov is allowed to use the team's workout facilities while suspended, and he has skated regularly after Kings practices under the supervision of an assistant coach.
The NHL reacted swiftly to Voynov's return to practice, which was hardly a secret with reporters and fans throughout the Kings' busy training complex.
"Such activity is in direct contravention of the terms of the suspension levied Oct. 20, which permit Mr. Voynov to use club facilities and work with team personnel but prohibit his participation in any team-related functions or activities," the NHL said in the statement announcing the Kings' fine.
Voynov will miss his 19th consecutive game when the Kings host the Bruins at Staples Center.
The Kings backed the NHL's suspension of Voynov even when it forced them to play with only five defencemen last month due to salary cap constraints caused by his absence. The league granted salary-cap relief to the Kings late last month, allowing Voynov's $4.167 million cap hit to be replaced on their active roster.
Voynov pleaded not guilty to the felony charge against him at his arraignment Monday in Los Angeles County Superior Court. His preliminary hearing is Dec. 15.