It all depends on the authority of an executive order, which is really very limited in establishing requirements.

I just heard Biden (5:00 on Jan 26, 2021) say that a quarantine is required at his Covid briefing. The executive order mandates a negative test and following CDC guidelines when returning from a high-risk country. That is almost all countries. CDC guidance say 7 days with a negative test, and 14 day of quarantine if you do not get tested.

Can this be enforced? Maybe by state law or possible Federal law. I doubt by Executive Order.

I am not a lawyer, but I have had develop many regulations to implement a lot of Executive Orders over my years of Federal Government service.