Want to explore the Solar System? Well you’re going to need to brush up on international space law before you leave the planet, and that means studying the “Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies.” Or, as most people refer to it, the Outer Space Treaty.

Signed in 1967, the Outer Space Treaty establishes a number of guidelines that nations should follow in order to explore space. The document touches on topics like appropriating space objects and how to prevent the contamination of other planets. It’s not a very comprehensive treaty, meant to be flexible in its interpretation. But more than 50 years later, with more than 100 nations party to the treaty, the agreement has ensured the peaceful exploration of outer space — and could continue to do so for many years to come.