First up, that’s not what execution of laws means. In regards to the executive branch, execution means for formal signing of bills I to law, and has nothing to do with actual enforcement.
Secondly, if he were to “enforce” it, it would basically be a DOJ recommendation to conduct and investigation and present a case to the Judiciary, which is likely to be go nowhere considering the current state of the US courts system. And every one of those steps takes time to do and that process then has to be repeated for every company that is doing business with Israel.