Treaties have and do grant the Federal government additional powers. They cannot diminish powers or add something that is taken away.
And non self executing treaties are meaningless they pretty much mean that the US government promised something but it is not compelled to do anything about it and there is no mechanism that would require it to comply.
The US constitution is supreme it takes precedence over anything the legislative branch might legislate and any action the executive branch might take.
Alien tort is also not accepted when interpreting the constitution so you literally cannot interpret the constitution from the point of view of international or foreign laws.
They obviously do not. If they did, you could basically abolish the Constitution with one with only the presidency, a bare majority of the Senate, and the cooperation of a foreign power. An actual Constitutional amendment must meet a much, much higher bar.
Congress does get extra power when a law is passed as a treaty. Issues that are state business under the 10th Amendment become federal business.
But it’s nothing like a constitutional amendment.
Are there potential circumstances where the US Constitution might conflict with obligations under the Rome Statute? Maybe; that certainly fairly regularly happens in practice with the Vienna Convention on Consular Relations, but the US has signed and ratified that treaty.
Not a great look.
I looked into it more and while 7 voted against, 21 abstained so votes don't tell the whole picture. Between China, Indonesia, India and The US you're talking a major chunk of the world population.
Anything China does is "a major chunk of the world population". Same with India.
The US government is not allowed to participate or facilitate a criminal prosecution that would deny a US citizen their constitutional rights there has been a Supreme Court case about this already ironically in 1998 which was also one of the triggers for voting no.
On a side note the ICC is terrible, any party can bring up a case, there is no separation of duties, no defined scope and no right of appeal.
The ICC is nothing more than virtue signaling, and should never been established in its current form the world was just too high on its own supply of late 90’s hopium at that point to care.
We actually were a signatory (and one of the prime movers for regularizing the ad hoc processes which we had also been a prime mover for creating in Yugoslavia and Rwanda) of the Rome Statute under Clinton, though the signature was effectively withdrawn under Bush.