Anyone with a space-worthy ship can travel in space. There are no restrictions, flight plans or planetary rules on who can travel where, except in the local space surrounding inhabited planets, space stations and the like. However, since a ship needs a Ship Heart in order to really class as 'space-worthy', and these are not so easy to obtain, actually coming into ownership of ship is not straightforward. Simply being on the crew of a ship is somewhat easier, though.
Once you're on a ship, you're good to go…. explore the stars! See the vast inky blackness! Discover what untold weirdness awaits on a newly terraformed planet! Well… until you find yourself 20 million miles from the nearest breathable atmosphere and your air recycler just broke down.
For these kind of reasons, the majority of regular legitimate spacefarers join the Spacefarers Guild, a loosely-connected mututal aid organisation for all types of spacefarer. By joining the Guild, you commit to aiding other Guild ships in distress when needed - but you also gain a commitment in return that you will be helped when in need (so long as another ship is close enough to help, anyway. The Guild makes no promises if you head off into uncharted areas alone). You also gain access to a network of Guild repair shops which charge reasonable prices with no haggling, and an information network that tries to keep everyone up to date on the latest known pirate ship IDs, meteor paths and other assorted threats. While Guild membership is on a per-person basis, not per-ship, it is common for either the whole crew of a ship to be members or none of them, rather than having mixed crews - to avoid confusion over who is eligible for help, if nothing else.
The Spacefarers Guild has so far managed to avoid being politically affiliated with any particular planet, political dynasty or other organisation of any type. As such, a Guild membership is currently recognised as a cheap and sensible form of insurance by the captains of both the meanest interplanetary skiffs and the most majestic intergalactic cruisers.
Of course, not all spacefarers are legitimate. For all of history, whenever there has been something worth wanting there have been people willing to go to any lengths to take it for themselves. Space travel is no exception, and despite numerous attempts to crack down from Cooperation members, piracy is rife and profitable within the galaxy.
Profitable piratical affairs naturally include the core piratical pillars of theft, smuggling, and murder, but with a wealth of information transmitted into the void so regularly, information trading and muscling in on high paying jobs are both highly lucrative pasttimes. It's quite common for one group of pirates to find an attractive pay-out only for multiple other pirate groups to land shuttles and argue (sometimes bloodily) over who gets to take the contract.
Though every pirate is a law unto themself, and every pirate ship is a law unto itself (and the captain on board), pirates have found it necessary to band together lest they be rooted out and dealt with one by one. As such, the Galactic Pirate Code is upheld by most pirates, and breaking it - while common - is a good way to get yourself left to asphyxiate in space next time you get in trouble with a Fjenician Phalanx Cruiser.
The Galactic Pirate Code consists of Five Tenets:
While pirates hold (loosely) to these tenets, attempts to organise pirates further have thus far all failed due to the immediate oneupmanship and infighting that inevitably occurs. Some captains have been known to gather large fleets together under their banner, but to call that truly “organised” would be a grave misunderstanding.