If the sanctions were never repealed by the US Congress, the US president has no right to overrule their policy. This has been in the US Constitution from the

If the sanctions were never repealed by the US Congress, the US president has no right to overrule their policy. This has been in the US Constitution from the beginning of the country and is hardly controversial. Interestingly, failing to uphold the Constitution and execute the laws passed by congress is serious grounds for impeachment (though it simply will not happen until at least 2023).