That's how I've come to view it as well, although perhaps from a different angle: it't not really a means of enforcing a UFP non-interference policy as such, but a means of preventing starship captains from enforcing their personal policies. The Federation Council isn't really all that worried about whether the development of the Capellan society will proceed in a manner approved by the Humane Society. It's worried about what James T. Kirk might do in UFP's name, perhaps dictating policy for the Council. If Kirk serves UFP interests well, then the few times he takes drastic action will not matter. But if Kirk does something badly at odds with Council interests, there exists this handy regulation by which Kirk can be thrown to Elba II and pumped full of compliance drugs.
Starfleet frontline forces must be allowed to work by "guidelines" rather than rigid operating instructions. But those guidelines have to be at least as powerful as military law in order to be effective, and the way the Prime Directive is construed is a good way to do that.
As for the issue of whether TOS and TNG directives differ, it's in some ways a futile argument. TOS was never self-consistent enough to offer a single, unambiguous description of the PD or its applicability, nor did it explore a sufficient number of scenarios to tell for sure whether 23rd century people would have reacted differently from 24th century ones.
Since TOS offers plenty of examples where the Feds show restraint when facing primitives or inferiors, but also examples where they tread softly with folks like Klingons, it's not all that different from TNG in practice. Rather, we can argue whether the TOS heroes showed restraint out of sheer pragmatism but the TNG ones because there was a directive about it, mainly because TOS didn't bother to namedrop the Prime Directive in such instances while TNG frequently did.
But back to the point suggested by hofner: when Kirk is seen "breaking the PD", that is, interfering where he perhaps shouldn't, about half the times he is acting under direct orders. If his superiors have told him to interfere with Capellans or Organians or Melkots, and he complies, the PD actually seems to be doing its real job admirably: Kirk is on a short leash. It's only in cases like "The Apple" or "Return of the Archons" where Kirk acts on his own that we might suspect Kirk is doing something "wrong" - but if the Council approves of it afterwards, then probably the PD was doing a good job again.
What we know for certain is that the exact wording of the PD must be verbose as hell, with all sorts of sub-clausules and appendices. It wouldn't surprise me at all to find that there was a provision for just plain ignoring all the interference limitations when either the superiors so command or the captain deems the summary waiving as compatible with current UFP policy.
Timo Saloniemi
