An old Washington operator, former Sen. Phil Gramm, has stormed back onto the scene to try to torpedo a key part of House Speaker Paul Ryan’s tax plan. Senate Republicans found Gramm’s takedown of the border adjustment tax so persuasive at a lunch meeting last month that Ryan himself had to clean up at the next week’s lunch. In a widely read Wall Street Journal op/ed, Gramm argued that the proposal would cost consumers and convulse financial markets. But Gramm failed to mention that one such victim of the tax change could be his own employer: a private equity firm, Lone Star Funds, whose extensive overseas holdings stand to suffer.Gramm, 74, said in an interview the firm doesn’t pay him to lobby and the policy’s impact on its portfolio isn’t clear.“I think our position is wait till we see a bill and then have lawyers look at it,” Gramm said. “My interest in the border adjustment tax has nothing to do with any specific economic interest. I think it’s bad policy.”Gramm said he is a vice chairman of the firm, working mostly in Europe and Asia.Gramm’s reappearance in the middle of a lobbying feeding frenzy had left allies and enemies alike wondering who he was representing. The former Senate Banking chairman is part of a growing class of influencers, many of them former lawmakers, who take advantage of legal loopholes to avoid publicly disclosing their activities. Gramm doesn’t have to register as a lobbyist if he’s spending less than 20 percent of his time lobbying. The law was written that way to avoid burdening corporate executives who occasionally contact a lawmaker, but it’s now widely exploited by former officials who charge clients fortunes to “advise” and “consult” but claim not to “lobby.”“You have people who aren’t registered who are doing these things, and unless someone drops a dime on you who’s going to know?” said Paul Miller, president of the National Institute For Lobbying & Ethics, a lobbyist trade group that wants to close the loopholes. “When people get caught and there are scandals, it’s going to be people like me who follow the laws who are going to get painted with that black eye.”Gramm’s Wall Street Journal article doesn’t mention his position at Lone Star, noting instead his affiliation with the American Enterprise Institute, a right-leaning think tank. Gramm said no one helped him write the article and he didn’t clear it in advance with his firm, but he did discuss it with a colleague at AEI.The Koch brothers are major supporters of the think tank and leading opponents of the border adjustment tax. A think tank spokeswoman said its donors don’t influence its research. Gramm said he doesn’t take a salary from AEI.Gramm fielded many calls in response to the Wall Street Journal article, including from some current members of Congress, he told POLITICO. (Some lawyers argue it doesn’t count as lobbying if the lawmaker initiates the contact.)Last week, Gramm met with Treasury Secretary Steven Mnuchin about the border adjustment tax, according to a person briefed on the meeting. Treasury spokesmen didn’t answer a request for comment, and Gramm declined to comment on the meeting.“I don’t kiss and tell,” he said.The Trump administration’s position on the proposal isn’t clear. Trump initially called it “too complicated” but later seemed open to it. Mnuchin has raised doubts. Commerce Secretary Wilbur Ross avoided taking a position in an appearance today on CNBC.Gramm’s firm, Lone Star, has investments in North America, East Asia and Europe, and has nine offices outside the U.S. The firm’s chief, John Grayken, renounced his U.S. citizenship in 1999 for tax reasons, according to Forbes. Last year, the firm raised $5.5 billion to buy mainly debt in North America, Europe, Asia-Pacific and Latin America, plus $5.8 billion to invest in commercial real estate debt and equity products in the Americas, Europe and Asia-Pacific, according to its website. Lone Star is in end-stage talks to buy most of Portuguese bank Novo Banco.“Lone Star has no position on the border adjustment tax and is not involved in any type of advocacy activity connected to the tax,” spokeswoman Christina Pretto said. “As far as Lone Star is concerned, Phil Gramm is free to express his personal views.”The border adjustment tax would hurt American people and businesses that own foreign assets because it would strengthen the dollar, making it more expensive to convert foreign profits, according to an explanation by the nonpartisan Tax Foundation. The plan taxes income from sales in the U.S. instead of domestic production; it would tax imports more and exports less than the current tax code.The proposal pits major exporters like General Electric, Boeing, Caterpillar and Pfizer against importers like Walmart, car dealers and oil refiners.While in Congress, Gramm fought for financial deregulation, including repealing the Glass-Steagall Act, blocking curbs on predatory lending and exempting derivatives such as credit default swaps — measures that Democrats often blame for precipitating and worsening the 2008 financial crisis. After retiring from the Senate, he became vice chairman of UBS Investment Bank.When Gramm taught at Texas A&M, one of his students was Jeb Hensarling, now chairman of the House Financial Services Committee.Nancy Cook contributed reporting.