The PD applies to unwarranted or unwanted intervention. If Starfleet is dragged into situations against their will by the locals, or if they are asked formally for aid, then the PD no longer applies.
Not really. Gowron requested aid during the civil war, under the terms of the alliance
, and still Starfleet refused, citing the PD.
Of course, Picard has a notoriously broad view of what the PD forbids him to do.