The prime objective of the Environmental laws is to protect the environment and form rules for the people on how to use natural resources. It exists at many levels and partly constituted by conventions, declarations and treaties. It is encompasses in the provisions of enactments laid down by the legislative bodies charged by the government with protection of the environment.

These laws are also based on certain important doctrines and legal theories which will help us understand the intent of the maker. In this article we will shortly overview the Public Trust Doctrine, Precautionary Principle and the Polluter�s Pays Principle with landmark case laws.

Public Trust Doctrine
The Roman Empire has developed this legal theory. The public trust doctrine primarily rests on the principle that certain resources like air, sea, water and the forest have such a great importance to the people as a whole and it is unjustified to make these resources subject to private ownership.

The said resources are gift of the nature and there should be available free for all. The doctrine enjoins upon the government to protect the resources for the enjoyment of the general public rather than to permit their use for private ownership or commercial purposes.

Various public properties including rivers, seashore and the air are held by the government in trusteeship for the uninterrupted use of the public so the government cannot transfer these properties to any private party who may interfere with the interest of public at large. The doctrine was first mentioned in M.C Mehta vs Kamal Nath[1].

In this case the Supreme Court applied the term public trust with regard to protection and preservation of the natural resources. The state government granted a lease of a forest land to a private company for commercial purpose but the area was ecologically balanced and rich with greenery. So the court held this kind of area cannot be granted on lease to a private owner for commercial gains.

M.I Builders Pvt, Ltd vs Radhey Shyam Sahu and Ors. [2]
Here the Lucknow Nagar Mahapalika or the Lucknow city corporation granted permission to a private builder to construct an underground shopping complex but it was against the municipal act and also the master plan of the Lucknow city. The court added that the land of immense value had been handed over to construct an underground shopping complex is a violation of public trust doctrine.

So the court held that there may be a public park which may fulfil the environmental necessity and use by the public at large.

Precautionary Principle
The precautionary principle has been evolved from Stockholm convention.In the developing countries like India , exploitation of natural resources is essential through industrial development while the international and national laws and the policies have already provided various guidelines regarding the term sustainable development which requires special attention to bring awareness aiming industrial and others who engaged in the exploitation of natural and manmade resources for economic progress. The principle implies that there is a social responsibility to protect the public from exposure to harm when the scientific investigation has found risk.

With a view to achieve this goal the honourable Supreme Court has not only explained the sustainable development but also imposed certain obligation to be followed by public at large.
In A.P pollution control board vs professor M.V Nayudu [3]and ors the Honourable Supreme Court held that the inadequacies of science at real basis that has led to precautionary principle of 1982.

The principle of precaution involves to prevent the environmental harm and taking some measures to avoid it. Environmental protection should not only aim at protecting health, property and economic interest but also protect the environment for its own sake.

This principle suggest that where there is a identifiable risk of serious harm e.g. wide spread toxic pollution, extinction of species and major threat to essential ecological process. In the above case, it was also held that there is a need to see that in he appellant authority under the Water Act and Air Act and the Hazardous Waste Water Rules 1989 should work properly and here the cases under Article 32 and 226 of the Constitution in the Supreme Court and High Court. It is also the duty of the sc to render justice by taking all aspects into consideration.

Polluter pays principle
It is a principle in the international environmental law where the polluter pays for the damage done to natural environment. It is also known as the extended polluter responsibility, whosoever is responsible for the damage to the environment should bear the cost associated to it. Its purpose is to shift the responsibility from the government to the public. It is a simple extension of the principle of fairness and justice.

To enhance the economic efficiency that is to protect the environment without sacrificing the efficiency of a a free market economic system. The additional revenues are used to cut income, pay role and corporate taxes. Revenues collected can help to achieve other social goals.

Some drawbacks of the doctrine are that ambiguity still exists in determining who the polluter is. It can cane difficult to measure how much pollution is produces. a large number of poor house hold informal sector forms cannot bear any additional charge for energy or for waste disposal. Pollution can be shifted to countries with weak legislation.

Conclusion
Under the doctrine of public trust the state has duty as a trustee under the Article 48A of the Indian constitution because it is the responsibility of the state to protect and improve the environment and safeguard the forest and wildlife of the country. The state�s trusteeship duties has been expanded to preclude a right to a healthy environment the court also included Article 21 of Indian constitution which signifies right to life of every human being under the territorial jurisdiction of the county.

The precautionary principle provides the policy makers with simple common sense approach to evaluate action .it allows for greater protection of the consumers and environment and requires decision makers to explain the rationale behind their decision and quantify the risks to provide objective information. The government also creates appropriate plans of action giving good information.

In the polluter�s pays principle the idea that the polluter should be made to pay for damages that they cause damage to the health of human beings and property of others in order to get free environment and sound working conditions, it is very necessary to introduce some guiding principles by the policy makers through government regarding environmental policies.

End-Notes:

1. 1997
2. 1999
3. 1999