The CDC's Four-Phase Plan

The CDC's Conditional Sail Order hinges on a four-phase plan for resumption of cruising. The four phases are as follows: 

1) Establishment of laboratory testing for crew in U.S. waters
2) Simulated voyages to test cruise ship operators’ ability to mitigate covid risks
3) Certification for ships that meet specific requirements
4) Phased return to cruising

Get Certified
While simulated voyages and establishment of laboratory testing were probably on order for the cruise lines regardless of what the CDC mandated, the certification process contains some teeth: 

Voyage-Length Restrictions
The certification process requires that the cruise ship operator must not sail or offer to sail an itinerary longer than 7 days. The CDC also reserves the right to shorten that duration as necessary.

It has been reasonably clear for some time that the initial voyages will be short jaunts to private islands, but, depending on how long this portion of the certification process remains in effect, it could impact the itinerary plans of some of the premium and luxury lines that usually offer longer sailings. 

Day-Of Testing
Much ink has been spilled over whether or not passengers will be tested on the day of embarkation or 1-5 days prior.

The CDC appears to resolve in favor of day-of, stating, "The cruise ship operator must conduct laboratory testing of all passengers and crew on the day of embarkation and the day of disembarkation in accordance with CDC technical instructions or orders.” 

A straightforward reading of that order implies that cruise ships will be required test immediately prior to embarkation, as has been done in Europe. 

Interestingly, the Healthy-Sail Panel argued that, while day-of-embarkation testing was beneficial, it was not a substitute for testing prior to passenger travel in the days leading up to the cruise.

This leaves open the possibility of passengers having to be tested twice: Once before they depart their homes for the cruise, and once at embarkation. 

It is also possible that either the CDC or the Healthy-Sail Panel will amend its portion of the recommendation. 

No Mention of Community Prevalence
Not mentioned was how the prevalence of COVID-19 in the community of departure could impact lines’ abilities to sail. In other words, if Miami has a particularly bad outbreak, there is, thus far, no “emergency break” that necessarily shuts down cruises from Miami. 

Nevertheless, the CDC gave itself broad authority to "modify these protocols as needed to protect the public’s health as required by CDC technical instructions or orders.”

Request For Information Results
The CDC also included a summary of results from its public RFI, or Request For Information. 75% of survey respondents advocated for reopening the cruise industry prior to a vaccine, while 25% advocated waiting until a vaccine was available. 

Survey respondents were in favor of conditions on the re-opening, however, with 85% supporting passengers wearing face masks, and 74% in favor of testing passengers prior to embarkation.

On the Same Page
After many months of well-documented acrimony, the CDC and cruise lines finally appear to be on the same page. 

While the CDC stressed the need for government oversight of the industry, its mandates closely echo the recommendations from the industry's own Healthy Sail Panel: Differences between the two are eminently bridgeable.

Furthermore, much of the negative language from previous no-sail orders was absent, with the CDC even going as far to say, "The actions taken by some cruise ship operators to improve their public health response to COVID-19 are encouraging."

By CDC standards, that's high praise indeed.