This Thursday, 28 ballplayers will step onto Brooklyn’s MCU Park baseball diamond wearing blue-and-white uniforms with “Israel” written across the chest, as they compete against Great Britain in the first round of the qualifying tournament of the World Baseball Classic, the sport’s equivalent to the World Cup. Win and the Israeli team will face either the Pakistani or Brazilian club, or both. The winner of the entire four-team, double-elimination contest will be awarded the 16th and final spot at the 2017 WBC, a partnership between Major League Baseball and the MLB Players Association.But of those 28 Team Israel players only two are Israeli citizens and both are pitchers: 37-year-old Shlomo Lipetz, and Dean Kremer, a 20-year-old Israel-American, minor leaguer for the Dodgers who was first Israeli ever drafted. The rest of Israel’s roster is made up of Americans who qualified under the WBC’s “heritage rule,” which, according to Peter Kurz, the president of the Israeli Association of Baseball, states that any player who qualifies for citizenship in a country is eligible to represent that country in competition.As far as my research has found, there is no official outline of the “lax” heritage rule, although the effort to link a player’s heritage has been covered before. According to 2011 article in The New York Times about Israel’s squad, “a player is eligible to join a team if a player is a citizen of the nation, qualified for citizenship or can hold a passport of that country. A player who has one parent who is, or was, a citizen of that nation, can also join that team.” This applies to other teams as well, but for Team Israel, there is an added malleability—a loophole of sorts—thanks to Israel’s Law of Return. This, in turn, allowed Kurz to choose from a larger pool of players.Major League Baseball players are eligible to play compete in the WBC, but they are unable to compete in this year’s qualifying tournament because the MLB season is still in full swing. This precludes Jewish players like Alex Bregman and Ryan Braun, for example. As a result, Kurz became into a curator of sorts, locating bar mitzvah programs, marriage certificates, and all types of Jewish-related artifacts that can prove his players’ Jewish lineage (and therefore eligibility).“Getting the Cohens and Goldbergs—that’s the easy part,” Kurz told me over sandwiches at an Upper East Side café. “But to win we needed to find the other guys.”Kurz spent the past six months keeping his ears open for tips. He routinely scanned websites like Jewish Baseball News and subscribed The Jewish Sports Review, a quarterly newsletter. He eventually compiled a list of 50 potential targets and had to verify the Jewish roots of each one.During our interview, he took out his laptop and cued up a folder of e-mails labeled “affidavits.” He clicked on a message from the mother of Ryan Sharriff, a left-handed minor league pitcher from the Cardinals. “This is her ketubah,” he said, pointing to an image on the screen. “Thankfully there’s a guy in MLB’s office that knows Hebrew and was able to translate it.”Kurz continued scrolling. He found a progress report from Hebrew School that the father of one of his players had sent him. He then opened a message from Corey Baker, a New York native and right-handed minor league pitcher, also for the Cardinals. A picture popped up of a 13-year old Baker, wearing a yarmulke and dark suit, and holding a Torah. “That’s from his bar mitzvah,” Kurz said. “I asked the family members for help,” he added. “It’s amazing what people find when they go looking through random boxes.”When I asked him what the strangest proof of lineage he ever received, he smiled, went back to his laptop and found a photo sent in by the family of Jared Lakind, a 28-year-old pitcher from Cypress, Texas. It was a tombstone with a Star of David carved onto it. “That’s Jared Lakind’s grandmother,” Kurz said. “After that all I have to do is prove that this is woman is actually Jared’s grandmother.”Kurz did, and so Lakind and 25 others are now free to suit up for a country in which they don’t currently reside, or have citizenship from. Kurz has already gathered all the paperwork. But they can now move their afterwards. The paperwork is all there, in a folder on Kurz’s computer.