Â鶹´«Ã½ — The space shuttle's return to earth for the final time marks the end of an era, but also opens an unprecedented age of private and commercial spaceflight. This new era will require international collaboration to keep watch over the practice, a University of Nebraska-Lincoln professor and internationally renowned space law expert said.

Frans von der Dunk said that in the short term NASA would be dependent on other countries' vehicles for manned spaceflights to the International Space Station. But in the long run, he said, this may be beneficial both for the United States and other countries.

"The result is a thorough stimulation of international cooperation, and the United States has still so much unique technology to offer that its dependence (on other countries) does not need to turn into a position of weakness," von der Dunk said. "International cooperation is fundamental for any true further development of international law, regulation and practice in the space sector."

Von der Dunk said the phasing out of the shuttle program, which completed its 135th and final flight Thursday when Atlantis touched down at Kennedy Space Center, has prompted private entrepreneurs to invest in commercial spaceflight.

Some companies -- like SpaceX of Hawthorne, Calif., an American space transport company founded by PayPal co-founder Elon Musk -- are close to launching their first flights. SpaceX, like other companies including Virgin Galactic, has critical U.S. involvement.

The legal implications for this new wave of commercial spaceflight are already becoming visible, von der Dunk said. The United States is leading the way in carefully developing a balanced regulatory regime for private commercial spaceflight on a national level, and also with considerable consultation with Europe.

"Soon, such questions will have to be addressed at a truly international level, where the same balanced approach between the interests of the operators in this infant industry to make things happen and the interests of the public at large regarding safety and security should somehow determine the details of such systems as well," he said.

Another international legal ramification involves security -- specifically, laws concerning export controls on "dual-use technologies," which can be used for both civil and military purposes, von der Dunk said. A sensible approach to current U.S. policies on ITARs, or International Traffic in Arms Regulations, will be important in that realm.

ITARs, which are interpreted and enforced by the U.S. Department of State, safeguard national security and further foreign policy objectives through the control the export of defense-related articles and technologies.

"The gradual progress in making the current U.S. regime on ITARs increasingly more sensible, efficient and effective is a very important step both for allowing relevant U.S. technology to serve those developments -- and therefore the U.S. industry -- and for allowing a more globally coherent approach to the security issues involved," von der Dunk said.