(FORTUNE Magazine) - Surrounded by traders chattering in Russian and staring at screens displaying the latest action on the Moscow bourse, the biggest foreign fund manager in Russia is plotting his next move.

But Bill Browder, who runs the $4.1 billion Moscow-based Hermitage Fund, isn't in Moscow. He's in London, working the phones to persuade Russian officials to let him back into the country after five months in exile.

Refused entry at Sheremetyevo airport in Moscow after a routine trip to Britain last November - he spent the night on a plastic bench before catching the first flight back to London in the morning - Browder now finds himself in a rented two-room office in Covent Garden, facing the hardball tactics the Kremlin usually reserves for native-born oligarchs who get in its way.

"They said my visa wasn't valid, and I thought it would be resolved two days after I got back on the plane," says Browder, recounting a tale that has echoes of Kafka as well as Gogol, the 19th-century Russian writer who chronicled the obtuseness of czarist bureaucracy.

But two weeks later Browder was told he was being kept out under Article 27, Item 1, of Federal Law No. 114FZ, which states, "Entry into the Russian Federation can be denied to a foreign national if it is in the interest of ensuring the security of the state, public order, or public health."

Browder - who grew up in the U.S., has British citizenship, and has lived and worked in Moscow since 1996 - isn't a spy, a political opponent, or the carrier of a dread disease. So why did the Kremlin say nyet?

The most likely explanation is Browder's hard-fought campaign for better corporate governance and more transparency at the companies in which Hermitage has big positions, especially energy giants Gazprom and Surgutneftgaz.

Hermitage has repeatedly sought a seat on Gazprom's board and exposed such dubious investments as chicken farms and Black Sea resorts; it has also sued Surgutneftgaz to clarify its convoluted shareholder structure.

"I stepped on someone's toes because of corporate governance, and this is the pushback from that," Browder says.

With Gazprom offering a new ADR to foreign buyers and Surgutneftgaz's management content to leave things as murky as a Siberian lake, there's plenty of incentive to keep a gadfly like Browder on the sidelines. In the meantime, Browder's long-distance management hasn't hurt performance - Hermitage is up 56 percent since his London exile began.

"Even so," says Browder, "Russia is my adopted home, and I want to come back."

Browder has appealed to British Prime Minister Tony Blair and the British Foreign Office, to the U.S. State Department, and to Russian officials like Minister of Economic Development and Trade German Gref, whom Browder buttonholed in Davos in January. But the agency that controls Russia's borders isn't budging.

"We've received a unanimous vote of support from government officials who are interested in investment, economic reform, and modernizing Russia," says Browder. "The trouble is, they're not the ones who control the visas."

The irony of the case - and what should alarm other foreign investors in Russia - is that Browder has been one of Russian President Vladimir Putin's biggest boosters, even defending the Kremlin's jailing of billionaire Mikhail Khodorkovsky and the dismemberment of his company, Yukos. If a Russophile like Browder isn't safe from Kremlin retribution, who is?

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