Unanimous, yes, but I am puzzled as to why the concurring opinions were written. I see no additional meat in them.
They are basically ‘passing the buck’............................
Its because of the history of this issue.
When Roberts became chief justice(2006) he wanted to address and limit the Corp and EPA's authority to use the CWA to regulate private property. This had been a problem since CWA had been enacted.
The case that was taken was called Rapanos vs United States.
The decision was split 4-1-4 with 4 conservatives, 4 liberals, and Kennedy being the 1.
In his opinion Kennedy used the phrase "significant nexus". Such as: if a body of water had a significant nexus to a regulated river, then it too could be regulated. But significant nexus is not well defined.
So subsequent to the ruling, lower courts would be ruling on subsequent cases and many conflicted decisions were handed down and some judges were publicly criticizing SCOTUS for their ill defined decision. Environmental lawyers and consultants were also complaining.
But SCOTUS would not take another case to clear it up. So, eventually McCarthy was appointed and she decided to rewrite the reg(2014) and it went into effect in 2015.
Maybe the rewrite would clear it up, and if not, it would put the issue back into the lap of SCOTUS forcing SCOTUS to clear it up.
The unanimous decision means yes, SCOTUS needs to fix the problem. The concurring opinions means that they disagree on how it will be fixed.