The NHL is reevaluating a completed trade between the Vegas Golden Knights and Anaheim Ducks because it might violate forward Evgenii Dadonov's no-trade clause, sources confirmed to ESPN on Monday.

The Knights had traded Dadonov, a 33-year-old right winger, to the Ducks along with a conditional second-round pick for defenseman John Moore and the contract of forward Ryan Kesler. The Ducks would select to receive Vegas' second-round pick in either 2023 or 2024.

But hours after the trade was announced, Vegas said it had "become aware of an issue with respect to the trade. We have been consulting with the league office."

The issue, the source said, surrounds a limited no-trade clause Dadonov had in his contract, which he signed in October 2020 with the Ottawa Senators. Dadonov's contract indicates he can't be traded without first submitting a 10-team no-trade list. The Ducks were on a previously submitted no-trade list.

Sportsnet reported that the list for the 2021-22 season had to be submitted by July 1, 2021, and that Dadonov believes it was.

But when the Golden Knights traded for Dadonov in July 2021, a source said, there was no mention of the trade protection on the trade call with the Senators and the NHL; therefore, it was not acknowledged when Vegas completed the trade with Anaheim on Monday, either.

The trade is now in dispute, with the NHL Players' Association having reached out to the NHL about its legitimacy.

Dadonov has 27 points in 62 games this season for the Knights, who acquired him for a 2022 third-round pick and defenseman Nick Holden in July 2021.

Monday's deal was a salary dump for the cap-strapped Knights; Dadonov is in the second year of a three-year deal and carries a $5 million cap hit. After burying Moore's salary in the AHL, Vegas stood to clear $3.375 million in salary-cap space.