Our military knows “freedom isn’t free.” Just ask any service member or veteran. Millions have served overseas, defending the freedom of our allies as well. Too many never returned. So while NATO expansion is generally a good thing, it must never be free. Collective self-defense spelled out in Article 5 means all for one, one for all. Considering NATO leaders recently agreed to accession talks with Montenegro as the 29th alliance member, we ought to ask the price. Even if few Americans ever heard of the tiny Balkan nation since it gained independence from Serbia in 2006, we’ll now be obligated to defend it. Though it’s not completely foreign — recognizable from the James Bond film “Casino Royale” — it is the Monte Carlo of Eastern Europe. So what’s the problem? Well, Montenegro, population 620,000 is notorious for easy money in real life too — particularly Prime Minister Milo Djukanovic. Even though he’s regularly accused of running a mafia state, he dismisses periodic mass protests as Moscow-inspired rabble rousing, orchestrated to keep the country out of NATO. Sounds plausible, right? Yet that theory falls apart considering all his pro-NATO critics. So before the dotted line is signed on Montenegro’s admission, Americans should know more about the prime minister and his inner circle. So here’s a glimpse: Mr. Djukanovic was implicated by Italy’s anti-mafia commission for a cigarette-smuggling ring which laundered over $1 billion in profits, according to court documents from Italian and Swiss trials. The only reason the Italians didn’t charge him directly is because of diplomatic immunity. After all, he is the head of state. Mr. Djukanovic was also ensnared in a telecommunications bribery scheme involving his sister Ana Kolarevic, a high-profile attorney, in which a Hungarian company, Magyar Telekom, acquired Montenegro’s state-owned carrier. Since Magyar trades on the New York Stock Exchange, it along with parent company Deutsche Telekom of Germany was forced by the U.S. Justice Department and Security and Exchange Commission (SEC) to pay almost $64 million in criminal penalties. As part of the settlement, Magyar admitted to paying about $9 million in bogus contracts to bribe “at least two government officials” as well as Ms. Kolarevic. Even more troubling, Dusko Jovanovic the editor in chief of the opposition newspaper, Dan, was gunned down outside his office in Montenegro’s capital, Podgorica. Despite the family’s lawyer asking the court to summon Mr. Djukanovic, that request was denied. But wait, there’s more. The Balkans, including Montenegro, have become the major hub for arms trafficking in Europe. The natural result of ample weapon stockpiles left over from the Yugoslav Army, lousy internal security, and a thriving black market. Not surprisingly, those weapons are falling into the hands of radical Islam-inspired jihadists. After the Charlie Hebdo terrorist attack in Paris last year, French authorities believed the Kalashnikov’s came from the Balkans. Representing just a tiny fraction of the estimated 4,000 military-grade weapons smuggled from locales like Montenegro into France. One Montenegrin citizen, 54-year old Vlatko V. was arrested in Germany headed to Paris with a rental car full of weapons and explosives just 8 days before November terror attacks. Coincidence? So considering all the downsides about Montenegro, why in the world would NATO accept such a liability? Because the alternative is worse. Since Croatia was admitted into NATO during 2009, Montenegro is now the only patch along the Adriatic Sea that isn’t part of the alliance. With the aggressive Russian Bear on the prowl and trying to reconstitute an empire, Moscow would love it as another Kaliningrad. That’s the small sliver of Russia on the Baltic Sea, wedged between Poland and the Baltic States, literally conquered and resettled by the Soviets after World War II. It’s a vital military stronghold right in the middle of NATO’s northern flank. Like Montenegro, Kaliningrad is also about the size of Connecticut. Given Montenegro’s strategic location and non-aligned status, from Vladimir Putin’s perspective, it’s ripe for the picking. And contrary to Moscow’s claim that NATO expansion is a threat to Russia, it is Mr. Putin’s regime that’s guilty of invading, annexing and threatening neighbor countries — not the other way around. Which is why NATO enlargement to include Balkan aspirants Montenegro, Bosnia-Herzegovina, and Macedonia makes sense. Ditto for Georgia across the Black Sea. Yet admission into NATO cannot be a license to steal. Beyond meeting military standards, Washington and Brussels must insist aspiring countries adhere to Western democratic values — including commitments to government transparency, free speech, rule of law and anti-corruption measures. Mr. Djukanovic must be sent a clear signal — NATO isn’t a “get out of jail free” card. Croatia’s former Prime Minister Ivo Sanader received a 10-year jail sentence for bribery-related corruption not long after his country’s admission. So while Montenegro’s admission to NATO should be a win/win, it must come with strings attached. Freedom isn’t free.