Sure, it depends on the disposition of the polities around you and how strong the police/defense force is. You could also run it with any system of government you like, libertarian or otherwise.
A lot of people in this thread are laughing at the Liberland folks for being doomed to fail, not realizing that "might makes right", etc. Well how would we be reacting if they became terrorists instead? Defended the area with homemade bombs? What if Jeff Bezos built a private army and decided to secede from the US?
The morality or intellectual interest of a people's claim to a territory (along with their chosen system of government) is completely orthogonal to their ability to enforce it. For the other end of the spectrum just look at Ukraine, as others here have pointed out.