Trump will face formidable challenges after withdrawing from the JCPOA. The first would be to establish a legal structure to reinstate sanctions against Iran.
What could be the US’ be up against? Will that work?
The USA is able to reinstate sanctions unilaterally at any time. There is still much anti-Iran sentiment in USA congress, particularly Trump’s Republican party. Trump is able to reimpose sanctions under existing legislation (Obama lifted sanctions by Executive order, which may be reversed). Trump may also ask the USA congress to impose new sanctions.
The USA requires no further authorization to impose sanctions on Iran. Such sanctions may not be liked by European countries, but they are not in a position to stop the sanctions. The USA may need to enforce sanctions against European countries that do business with Iran.
Ultimately it is not certain that the tactic will work. May sources indicate that Iran’s economy is basically fragile resulting from Iran’s large investments in exporting conflict, particularly in Syria, which if true may make Iran’s leadership more willing to compromise in order to avoid economic difficulty.