As a follow up from Madhav's post, I think that terms like 'judicial activism' can hide more than they reveal. One needs to be careful about the precise judicial role where the court is being accused of being activist. PIL is strictly a standing issue, and the only relevant question at this stage is who should be allowed to bring in an action. The various possibilities, using Cane, include (a) direct and sufficient interest standing, (b) associational standing (where a group of persons having direct and sufficient interest is represented by an organisation or person), and (c) public interest standing (where the petitioner represents the public interst).
All three categories involve different issues. It is crucial in (b) that the representation is authorised in some form by those represented - Cane calls for a 'democratic stake' by those represented in the association. The simple idea is that the association needs to have some basis on which it claims to represent my interest. This category is similar to class-action suits.
In (c), on the other hand, it is important that if public interest standing is to be allowed at all, the petitioner must do a good job of it. It is much better to not allow an inexpert (if well-intentioned) petitioner bringing in a badly argued case which creates bad precedent since it does more harm than good to the public interest. Of course the boundaries between (b) and (c) are fuzzy and there will be overlap. Was the Narmada Bachao Andolan case about associational standing or public interest standing? Rules need to be evolved for these hybrid cases, but it does not detract from the basic distinction.
Justiceability, on the other hand, is a concept distinct from standing, and should arguably apply equally to whoever brings the action. Here one has to consider whether there is any area of law which is completely inaccessible to the judiciary. I personally believe that once a violation of fundamental rights has been made out, the Court has no option under Article 32 but to consider it as justiceable - although it can accord limited deference to the Executive or the Legislature, depending on the subject matter. A good example of a case which was (wrongly) thrown out at entry stage on justiceability grounds even though it involved important fundamental rights issues was Ahmedabad Women Action Group (involving constitutional challenge to personal laws). Hunt argues against the spatial concept inherent in any talk of 'areas of deference' and says that no case can be a priori judged to be non-justiceable if it prima facie involves fundamental rights violation. The degree of deference due is a judicial decision that needs to be decided on the facts of the case, and not at the entry stage itself. Deference is obviously connected with the issue of the appropriate standard of review.
Justiceability should also be distinguished from a (legitimate) screening method used at the entry stage - whether a prima facie case has been made out (or, in other words, whether the petitioner has any chance of success) is a distinct and legitimate resource management consideration.
Finally, activism in the context of remedies is also an entirely separate issue, and one has to consider the question in the context of Article 142 ('complete justice' requirement).
When talking about judicial activism, we need to be clear in what context we are discussing it. A Court may be 'activist' on standing and remedies, which being retrogressive on standard of review.
(Comments, as always, are welcome, from stray and astray readers alike)