This time it once more does not seem to be an economic advice. However, in some regard lawyers and economists make the same mistake. When they have to discuss an issue and at best provide some conclusion or judgement, they choose a certain framework as given and claim their implications as positive results. Though, as long as these frameworks are built on definitions and assumptions, it is normative. So, even if their results are derived and documented by complex analytics or finest verbalism and citation, they have to be considered as normative as well.
Of course, that does not imply that these results are automatically wrong. However, it has to be accepted that they can be criticised just by normative arguments, because in the end they are not more than that too. That something is established and considered as law or common sense therefor is not a giving of evidence for its legitimacy. The latter always can and have to be taken in question.
So whether a compulsory acquisition is an illegitimate measure depends whether the property was accumulated legitimately – not just legally. Similar thoughts can be seized about the height of market based income, the sentence on tax evasion and the judgements on political corruption. No one is above the law, but in the end the stated law is not naturally given. It is nothing more than a temporary chosen framework, built on normative definitions and assumptions – just like the mainstream economic theory – and most important: it can be corrected.