The ruling came as Fitch Ratings agency became the third major international ratings agency to downgrade its expectations for TNK-BP over the oil firm's fierce shareholder dispute.
Dudley is managing TNK-BP from abroad after he left Russia last month amid the dispute between the British major and a quartet of Soviet-born billionaires, who own the other half of Russia's No. 3 oil producer.
"The court ... has confirmed the fact that TNK-BP's Robert Dudley has committed a violation and has been fined," TNK-BP said in an e-mailed statement.
Dudley was fined 500 rubles ($21), a court official told reporters after the hearing.
The court case over labor violations could have ultimately seen the BP-nominated chief executive barred for three years.
The case, initiated by the State Labor Inspectorate, raised questions about TNK-BP's use of foreign employees. BP's local partners have also complained about the use of foreign workers and secondees from BP.
TNK-BP's shareholders are locked in a public battle over strategy and management at the firm, which produces one-quarter of BP's global output.
The Russian side of the firm has demanded Dudley's resignation, accusing him of poor performance and favoritism toward BP.
Dudley, who left Russia after failing to receive his visa and saying he and the company were subject to a campaign of harassment, has not disclosed his whereabouts.
Reviewing its outlook for TNK-BP, Fitch Ratings agency said in a statement that it had placed TNK-BP on rating watch negative and may cut its BBB- rating on corporate governance concerns and the shareholder conflict.
"The [rating watch negative] reflects Fitch's concern over continued deterioration in TNK-BP's corporate governance, resulting from the ongoing major shareholder conflict, as well as its potential credit impact," it said.
Earlier this week, Moody's Investors Service downgraded its outlook for TNK-BP to "developing" and Standard & Poor's lowered its long-term corporate credit and unsecured debt ratings.
"Fitch is also concerned about the impact of the dispute on TNK-BP's ability to remain on track with the development of its new fields, both in terms of investments and implementation, including adequate staffing," Fitch said.
TNK-BP's chief financial officer, James Owen, resigned Aug. 4, citing a conflict between BP and its Russian partners, grouped in the Alfa-Access-Renova consortium.
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