Well, I’m not sure since France is a major ally and would be deeply upset. There was a somewhat similar situation with Andrew Lester, the Max Factor cosmetics heir that raped over a hundred women. He fled while out on bail, to Mexico. Now, Mexico has no problem extraditing Americans back to America as long as they won’t be sentenced to death. But Mexico also isn’t going to spend tons of money and man hours searching for American fugitives who are hiding in their country. This was essentially the situation with Andrew Luster. He ended up living fairly openly in Puerto Vallarta, some have suggested probably with the complicity of local officials who may have received bribes.
Anyway, a U.S. bail bondsman (whose licensure has no legal authority in Mexico) went after him and captured him. This was considered kidnapping under Mexican law. He was escorting Luster back to the United States when he was captured by Mexican authorities. In this scenario, the bounty hunter was charged, and Luster was extradited to the United States. While they weren’t interested in doing the leg work, the Mexicans had no problem with extraditing him when he literally fell into their lap. FWIW the bail bondsman was granted bail and then fled Mexico, himself becoming a bail jumper. Mexican authorities requested his extradition, and he was taken into custody by U.S. Marshals and put on ankle monitoring while the legal fight played out. During the subsequently legal battle he became a cause celebre, with a large number of U.S. Congressmen coming to his defense and formally passing a resolution requesting Mexico drop the charges. Possibly due to political pressure, the Mexican government simply allowed the case to expire on procedural grounds and the bounty hunter essentially got off completely from any criminal penalties.
There was another situation somewhat similar, Fawaz Youniz was a Lebanese Hezbollah member involved in hijacking a Royal Jordanian airline flight in Beirut with 70 passengers (4 Americans) on board. He escaped after the hijacking to Cyprus, where American officials were aware of where he lived. The FBI turned one of Youniz’s friends, and said friend lured him to a party on a yacht. The yacht had been rented by the FBI, and the party goers were all FBI agents. Once the yacht passed into international waters he was arrested, put on an aircraft launched from an aircraft carrier and flown directly to the United States. He was prosecuted for the hijacking and convicted, spent 16 years in prison and was then deported. I don’t know of any diplomatic response from Cyprus, but Cyprus isn’t France.
In the scenario of Polanski being illegally kidnapped from France and dropped in Times Square, I think a lot of complex issues would be set in motion. For one, he’s not wanted in New York, but in California. Likely his extradition hearing from New York to California would be a large political affair, much would depend on the official position of the State Department and possibly the President. If they wanted to return Polanski as a courtesy to France, they’d apply pressure on New York to not extradite him to California, but to release him on some pretext so they could ship him back to France. Whether that would happen or not would possibly depend quite a bit on how much of a row France wanted to make over it. While Polanski has received defense from some of the French elite, I believe the last time he was detained on threat of extradition (in Switzerland), a large chunk of the French public was polled as thinking he should be extradited, so he’s less popular with the public at large than with the elites.
There’s also a question of Federalism. The Federal government would, as far as I know, only be able to apply political pressure on New York. If the New York courts extradite him to California, the Feds would then apply political pressure to California to release him–but I don’t know if there is actually a mechanism by which they can force the matter. I know that in the case of some foreign nationals who have been executed in the United States, the State Department has tried in the past to apply pressure to the State government’s involved, and been unsuccessful–State simply lacked legal authority under our laws to force the States involved to do anything.