If it were up to Elon Musk, the SpaceX team would have far more foreign scientists working with their American counterparts to send the first permanent colonists to Mars. Unfortunately, it’s not up to him. Rocket science falls under International Traffic in Arms Regulations, which prohibits companies that deal in military technology (rockets and anything going to space included) from hiring foreign workers. During his speech at the International Astronautical Congress in Guadalajara, Mexico, on Tuesday, Musk responded to an audience member’s concern that the company only hired Americans.

“I think people are a bit confused about this; unfortunately, this is not up to us,” Musk said. “U.S. Government regulations make getting a job in the U.S. hard enough as it, but if but if you’re working on rocket technology, that’s considered an advanced weapons technology, so even a normal work visa isn’t sufficient unless you get a special permission from the Secretary of Defense or the Secretary of State. So I want to be clear, this is not out of some desire of SpaceX to just hire people with green cards.”

Still, if Musk really wants to create a space railroad to Mars, it’s going to take some international cooperation. SpaceX is off to a great start conceptually, and its American technicians are certainly the best of the best, but Musk knows there are other great scientists out there.

“I think that this is not a wise policy for the U.S., because there are so many talented people all around the world that would love to have worked at our company, but unless they can somehow get a green card we’re legally prevented from hiring anyone,” Musk said. “I wish we could do more, but our hands are tied.”

He’s right — the United States has a long history of inviting foreign scientists into the country to work on military or space endeavors, and it hasn’t been too scrupulous about it in the past. The most notable example is Operation Paperclip, the Office of Strategic Services (the CIA before there was a CIA) program that brought over 1,500 German scientists to work on high-tech military projects directly after World War II. Essentially, as soon as the war was over, the OSS started recruiting the Nazi’s top rocket scientists and bringing them to the U.S. to make weapons and start the fledgling space program. The OSS created fake names, biographies, and credentials for scientists like Wernher Von Braun to get around President Truman’s prohibition on, well, directly hiring Nazis, so really the least the federal government could do is give Musk a break and let SpaceX hire from the international scientific community (very few of whom are Nazis, for the record).

It’s possible that as SpaceX continues to innovate on Earth with ideas like intercontinental shipping, the government will get wise to the annoying restrictions and find a way to loosen regulations. It’s also worth noting that this problem does not apply to Tesla, because the electric car company isn’t making rockets. Musk said that around 30 percent of Tesla’s engineering team is foreign nationals, so it’s pretty clear that he doesn’t have a grudge with non-Americans. After all, he’s a South African-Canadian-American, so any multicultural bigotry would be more hypocritical than hiring 1,500 Nazi scientists after spending 10 years trying to defeat them.

Photos via SpaceX