Same principle on why DAP is not criminal.
What they lost on was that (ironically) there had never been a 3rd Amendment Case before. Because of that the government had no way of knowing, for sure, that their actions were indeed illegal. Therefore the defendants were covered by a qualified immunity unless they knowingly acted illegally; and in the absence of previous precedents on this issue, the standard of “knowing illegality” was not met.
Source: (6) Home – Quora