The man who helped write the book on creating a federal Muslim registry in the name of national security, now has Donald Trump’s ear as a top member of his transition team.

Kansas Secretary of State Kris Kobach, a policy wonk with a reputation for handcrafting the legal means to political ends, says he has a plan to help Trump pull off some of his most contentious campaign promises.

Trump has explored a variety of methods to vet potential terror threats, targeting specifically Muslims by proposing outright travel bans or creating a federal database of all people in the United States who practice Islam.

Kobach believes Trump can take action immediately with the swipe of a pen. In an interview with Reuters this week, Kobach said Trump's immigrant transition team proposed drafting executive actions to reinstate a post-9/11 era program that registered immigrants and visitors from countries designated as havens for extremist activity.

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Kobach would know — he helped write the blueprint for it while working for the Justice Department under President George W. Bush.

“These programs had Kobach’s signature all over them,” said Muzaffar Chishti, director of the non-partisan think tank the Migration Policy Institute. "Now, the architect of the old program again has a seat at the table."

Kobach is renowned as the mastermind behind the Republican Party's heavily contested anti-immigrant bills and restrictions on voter registration.

Kobach first met Trump days before the New Hampshire primary, the Kansas secretary of state said last month in a podcast with Politico’s Glenn Thrush. The policy savant said he offered his services in helping Trump nail down the details of his immigration platform.

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But Kobach soon had his fingerprints all over Trump’s policy white papers. He even found a potential way to pull off even Trump’s most far-fetched of campaign promises — like forcing the Mexican government to write a blank check to build a massive wall along the U.S. border.

Using a technicality tucked within the Patriot Act, Kobach plotted a way to force Mexico’s hand by holding hostage the millions of dollars that Mexican nationals in the U.S. send home to family each year.

Kobach is now on a tour touting himself as the brains behind the border wall payment plan. And with Trump assembling the final pieces of his cabinet, Kobach has indicated he may have another trick up his sleeve.

The National Security Entry-Exit Registration System, or NSEERS, targeted people from 25 countries that were considered "higher risk" of extremist activity. The program focused only on young men over the age of 16, who underwent intense interrogations. An earlier iteration asked for Muslims to come forward and identify themselves, provide fingerprints and personal information.

Chishti says the registry was broad by design. Rather than discriminate people by religion, the program instead focused on all people from Muslim-majority countries.

“There is no way of establishing a registry of Muslims because there is no way of establishing who is a Muslim and who is not,” he said.

President Obama shut down the operations in 2011, but the policy infrastructure technically remains on the books. Trump could simply revitalize the program by designating which countries were deserving of the "extreme vetting" of all individuals, Muslim or not.

The DHS Inspector General later issued a report finding that the program was costly and unreliable. More than 80,000 men participated in the registry. Thousands of those were interrogated and even detained. None were ever prosecuted on terrorism charges.

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Instead the program created a pipeline for deportation. More than 13,000 men were removed from the country for either overstaying a visa or being unlawfully present in the U.S.

Fahd Ahmed, executive director of New York-based Arab and south Asian advocacy group DRUM, said the program had a lasting impact on Muslims who soon grew accustomed to being targeted for interrogation at airports.

“For thousands of people, families were destroyed, livelihoods were destroyed, the social fabric of our communities — destroyed,” Ahmed said.

And Kobach’s new proximity to the power structures in a future Trump administration has top Democrats sounding alarms that he is unfit to serve.

Rep. John Conyers issued a statement on Wednesday railing against two Trump advisers — Kobach and Frank Gaffney, founder of the hard-right Center for Security Policy — for being “right wing extremists.”

Conyers took particular aim at Kobach’s tenure at the Justice Department and his blueprint for a Muslim registry, calling it "a proposal that flies in the face of the constitution and is a threat to the civil liberties of all Americans."