The jury is an old form of democracy. The king/government can make what laws they like, but it needs to have enough popular support that a jury will freely choose to convict according to it.
Of course, like all forms of democracy, the outcomes don't always agree with your or my sense of justice.
> it has to be balanced against crimes that are in principle clearly wrong
In this system, whoever gets to decide what is "clearly wrong" has the real power.
The jury is an old form of democracy. The king/government can make what laws they like, but it needs to have enough popular support that a jury will freely choose to convict according to it.
Of course, like all forms of democracy, the outcomes don't always agree with your or my sense of justice.
> it has to be balanced against crimes that are in principle clearly wrong
In this system, whoever gets to decide what is "clearly wrong" has the real power.