As you may already know, today the International Court of Justice ordered the United States to lift new Iran sanctions. The news headline says:
The UN’s international court of justice has reprimanded the US over its re-imposition of sanctions on Iran, ordering Washington to lift restrictive measures linked to humanitarian trade, food, medicine and civil aviation.
And in response,
The US secretary of state, Mike Pompeo, reacted by announcing the US was terminating the treaty.
I wasn't able to find any detailed explanation about 1955 Treaty of Amity. Wikipedia does not have any information about it, and it is not even on the compiled list of treaties (which looks odd).
But I read on some other news that there is an Article in the Treaty which says that each party's withdrawal has to be notified one year in advance, which means today's withdrawal does not nullify the ICJ's vote.
Regarding the other questions such as this one which led to the conclusion that withdrawal from a treaty that was approved by the Congress has to be approved by the Congress itself, I have two questions in mind:
Was this treaty approved by the Congress or the Senate? And in that case, does it mean treaty's termination also requires the Congress/Senate approval?
Does the US withdrawal nullify the ICJ's vote?