The title is a bit misleading. Off label sales are not illegal. At question is off label promotion by company sales reps. The ruling looks narrow intitially and covers the truthful verbal discussion of a drug's off label use by a sales rep on an office call. In this particular case the rep was responding to questions asked by an undercover agent. Unclear is whether this will extend to other promotional material such as advertising to clinicians and the public.
reps can't discuss anything off-label even if asked. They cannot talk about p2 trials, p3 trials, potential indications, etc... Off-label use by a physician is completely legal however. Insurance will usually stop a product from being used if it is not for the approved indication so the physician would have to say it is being used for the approved indication for the patients insurance to reimburse.
This court ruling remains in a grey area and may be headed to the Supreme Court. FDA will certainly object as will the Justice Dept. Companies cannot deviate from the package insert in their promotional materials. However, salesmen who are trained about the pipeline of additional indications may be speak about them. Perhaps they can refer to third party publications on phase 2 trials. What is termed "legal" is whether the drug is approved or not, rather than approval for a specific indication. This was a test case set up by the pharmaceutical industry who are tired of paying hefty fines for what has become a normal and customary practice.