There are three kinds of ignorance.
The first is genuine ignorance: The person honestly did not know.
The second is culpable ignorance: The person was capable of finding out but did not find out by sheer negligence.
The third is deliberate ignorance: The person knows that there is something they should find out about but decides to keep themselves in the dark – perhaps in the hope that being ignorant might excuse lack of required action.
All three kinds of ignorance could lead to varying degrees of legal liability.
Out of the three, deliberate ignorance could have the most serious legal consequences as in certain cumstances it could amount to fraud.