In bitcoin network, there is a general rule, always the longest chain should be accepted as a valid on. However this is just one implementation of a so called fork resolving strategy which might be extended and generalized on a long run. Such extensions might include:
- instead of just chains, considering the whole weighted structure of the possible forks, like in Ethereum taking also uncle or omar blocks into account.
- in a permissioned chain, blocks might be prioritized and weighted based on the fact who signed them.
- in an attempt to avoid selfish mining, the blocks might be weighted with the creation time.
Further implementation and algorithms might be also possible, it is only important to note that fork resolving strategy as taking always the longest chain is only one possible implementation.