If you are entering Costa Rica and Panama via a land border, you just need a bus ticket out for the country you are about to enter..though as above points out, a flight reservation will suffice.
Does that mean that if you enter with a motor vehicle you still need a bus/air ticket out? Wouldn't that imply that you would import the motor-vehicle permanently and illegally?
I don't know what the law says, but the need for a bus/air ticket for everyone crossing a landborder seems completely ridiculous to me (which of course does not mean it's not true). I certainly have a hard time believing this is true when crossing with a motor vehicle. And if not needed with a motor-vehicle why would someone with a non-motorized vehicle be treated differently? Or even someone crossing on foot?
If entering by public transport the demand for a ticket out seems much more reasonable. I can however imagine that third country pedestrians/cyclists are so rare that they are not considered in the law or due to ignorance by officials treated the same as people on public transport. (making it a practical rule, not an official rule)
Has anyone the exact text from the applicable law at hand?