Case in point Siachen as well.
Last para, Clause (ii) to the Shimla agreement states that the line of control resulting from the ceasefire of December 17, 1971, shall be respected by both sides without prejudice to the recognised position of either side. Neither side shall seek to alter it unilaterally, irrespective of mutual differences and legal interpretations. Both sides further undertake to refrain from the threat or the use of force in violation of this line.
The problem with Siachen was that LoC was not marked there. It was not defined if Siachen was inside Indian side of Kashimir or inside the Pakistani side. So when IA occupied the post, it was not altering LoC, simply because it did not exist. So legally, India did not violate Shimla agreement by occupying Siachen.
My point being that any commitment or agreement between any nation is for all intents and purposes 'non-binding'. If India were to violate the IWT tomorrow, even if arbitration gave a decision in Pakistan's favor, there is little Pakistan could do short of going to war to make India adhere to the decisions made by the mutually agreed upon arbiter.
This is why this 'non-binding' argument often raised by Indians is just a canard. The fact is that when India and Pakistan both agreed with the UN resolutions on Kashmir, they essentially entered into an agreement and commitment on the status of the territorial dispute and how to resolve it. That agreement is just as binding, or non-binding, as any other agreement India or Pakistan entered into or will enter into, so pointing out 'non-binding' is moot.
You can call this argument of non-binding as canard and you can call it moot. Thats mere rhetoric. The legal case is however strong in Indias favour.
As with the commitment issue, if the UN resolutions are going to be the basis for Kashmir solution, then just as India is obligated to hold plebiscite, Pakistan is equally obligated to remove all her tribesmen out of P0K. In fact, the plebiscite is subject to complete removal of these tribesmen, which after 60 odd years is a near impossible task.
Anyway, it seems to me that you are warming up to the fact that UN resolutions are useless piece of paper and the true solution lies in mutual discussions. Nice to know that.
how exactly can an international court or arbiter enforce any decisions?
It appears that UN can and has in the recent past enforced its powers. In East Timor. UN maintained a civil administration for about 3 years, till its independence. A coalition of troops, lead by Australia, were stationed there during that time.
I fail to see how you could come to that conclusion given the first clause of Simla;
(i) That the principles and purposes of the Charter of the United Nations shall govern the relations between the two countries.
On the contrary, since Simla explicitly speaks of the UN charter and principles 'governing relations' between the two countries, and at no point speaks of, or implies, circumvention or supersession, the mutually agreed upon and endorsed UNSC resolutions continue to be valid.
Since this is not the last time that you are going to make this non-sequitur argument, let me take a one last stab at it.
Governing of the relation between two countries is not same as resolving of a specific conflict. International relationships involve trade, commerce, tariff, co-operation on any other economic or non-economic issues like resource sharing, immigration, security etc. As per Clause (i) to the Shimla agreement such issues are to be dealt with, within the basic framework of UN Charter i.e. governed by UN Charter. In case of any conflict, which may arise in maintaining such relationship, it is to be resolved as per the Clause (ii), i.e. through mutual agreement. Thus if any UN resolution exists and one party is desirous to resolve issues through such existing resolutions, the other party will have to agree to it.
It is a different matter if India wants to violate those agreements and renege on its commitment, which is essentially what it is doing, but then call it what it is.
As to implementing the modalities of what the UNSc resolutions demand, that issue can be broached once India decides to review its decision of violating its commitments and agreement, mere statements about the possibility, or not, of this or that does not make it so.
Indias commitment comes into play only after Pakistan has fulfilled her commitment. Good luck with that.
The only arguments that you have made so far, are all appeals to emotion. When it comes down to the hard fact of law, India is on pretty solid ground.