So argues Prof. Jack Goldsmith (Harvard) in his Executive Functions post. An excerpt:

The United States in the MOU pledges "immediately" to "issue waivers for export of Iranian crude oil, petroleum products and derivatives, and all associated services, including banking transactions, insurances, transportation, etc." (Emphasis added here and throughout.) These waivers presumably include waivers of U.S. statutory sanctions against Iran.

I don't think the president has the authority under domestic law to issue these waivers. The Iran Nuclear Agreement Review Act (INARA) of 2015 applies here and temporarily bars a president from waiving sanctions against Iran. The executive branch has counterarguments, to be sure. And it's doubtful that any institution will make the president comply with INARA in any event….

Read the post for much more.