“You need to be prepared to spend money to get access at events like this,” Mr. Vanetik wrote to Mr. Fuks in a text exchange cited in the lawsuit.

According to the lawsuit, after Mr. Fuks repeatedly requested a refund to no avail, Mr. Vanetik threatened in a phone call to use his influence in Washington to restrict Mr. Fuks’s travel to the United States.

“Not long after” the call, according to the lawsuit, Mr. Fuks “had his visa revoked and a five-year travel ban instituted against him.” The travel restrictions, which remain in effect, could complicate his ability to offer testimony in the lawsuit.

The complaint, filed by the international law firm Dentons, offered no proof that Mr. Vanetik played a role in Mr. Fuks’s travel restrictions. It accused Mr. Vanetik of fraud, breach of contract and other transgressions.

In an interview in March that will be featured in an upcoming episode of The Times’s television show, “The Weekly,” Mr. Fuks recalled Mr. Vanetik describing the ticket-acquisition rules as precluding purchases by foreigners, and suggesting Mr. Fuks instead “send him the money to buy them.” Mr. Vanetik said, according to Mr. Fuks, that he could “even get them for $50,000 less” than the $250,000 asking price. “I said that was fine,” Mr. Fuks recalled, “and transferred the money.”

In an interview, Mr. Vanetik categorically denied threatening Mr. Fuks or working to restrict his travel. Mr. Vanetik said it was actually Mr. Fuks who made threats about consequences if his money was not refunded, and said, “I regret having had any contact with such a questionable and confrontational person as Fuks.”

Mr. Vanetik, a lawyer, said the $200,000 payment was at least partly for legal work conducted for Gennady A. Kernes, an ally of Mr. Fuks’s and the mayor of his hometown, Kharkiv, Ukraine. Mr. Vanetik said he “never intended to use Fuks’s money to buy tickets from the inaugural committee.” Instead, he said he referred Mr. Fuks to a lobbying firm “that tried to arrange for him to attend an official inaugural ball as a guest,” and also arranged a program of inauguration activities that were sponsored by groups other than Mr. Trump’s inaugural committee, which Mr. Fuks approved, according to Mr. Vanetik.