The Constitutional and Legislative measures
Our fundamental duties and directive principles have made it a constitutional mandate to protect and improve the environment. It is the country's commitment to the ideas of a welfare state. The Indian constitution contains specific environmental protection provisions in the chapters of the State Policy and Fundamental Duties Directive principles. In recent times, judicial activism has revealed the absence of any specific provision in the Constitution recognizing the fundamental right to a (clean and healthy) environment.
A global adaptation awareness for the protection and conservation of the environment in the seventies inspired and encouraged the Indian Government to enact the 42nd Amendment Act (1976) to the Constitution. The said amendment added Art. 48A to the Directive Principles of State Policy. 
It Declares: -
“the State shall endeavor to protect and improve the environment and to safeguard the forests and wildlife of the country”.
A parallel duty is levied upon on every Indian citizen in the form of ‘Fundamental Duty’ –
“to protect and improve the natural environment including forest, lakes, rivers and wildlife, and to have compassion for living creatures”.
Certain amendments were also introduced in the Seventh Schedule of the Constitution to bring about particular changes. For instance, ‘Forest’ and ‘Wildlife’ were transferred from the State list to the Concurrent List. 
This clearly depicts the concern of the Indian government to prioritize the protection of the ecosystem and brought it under the tag of national agenda.
Directive Principles, though not enforceable by any Court of law have been cited by Court bench numerous times, and these judgements suggest that they are complementary to the fundamental rights.
In several environmental cases, the courts have guided by the language of Art. 48A. and interpret it as imposing “an obligation” on the government, including courts, to protect the environment.
In L.K Koolwal v. State of Rajasthan, a miscellaneous writ petition by Jaipur 's citizens forced the municipal authorities to provide adequate sanitation. The court observes that when every citizen has a constitutional obligation to protect the environment under Art.51A, the citizen must also be entitled to enlist the assistance of the court in enforcing this obligation against recalcitrant state agencies. The Court gave the administration six months to clean up the entire city and rejected the plea that there was no funding and no staff. 
The Public Trust Doctrine, evolved in M.C. Mehta v. Kamal Nath, states that certain common properties, such as rivers, forests, seashores and air, have been held in trusteeship by the government for free and unimpeded public use.  Granting a lease to a motel on the banks of the Beas River would interfere with the natural flow of water and the State government violated the doctrine of public trust.
A matter regarding the vehicular pollution in Delhi city, in the context of Art 47 and 48 of the Constitution came up for consideration in M.C. Mehta vs. Union of India (Vehicular Pollution Case). It was held to be the duty of the Government to see that the air did not become contaminated due to vehicular pollution. The Apex court again confirming the right to healthy environment as a basic human right stated that the right to clean air also stemmed from Art 21 which referred to right to life. This case has served to be a major landmark because of which lead-free petrol supply was introduced in Delhi. There was a complete phasing out old commercial vehicles more than 5 years old as directed by the courts. Delhi owes its present climatic conditions to the attempt made to maintain clean air.
The Ganga Water Pollution case: M C Mehta V. Union of India, AIR 1988, SC 1037
The owners of some tanneries near Kanpur were discharging their effluents from their factories in Ganga without setting up primary treatment plants. The Supreme Court held that the financial capacity of the tanneries should be considered as irrelevant while requiring them to establish primary treatment plants. The Court directed to stop the running of these tanneries and also not to let out trade effluents from the tanneries either directly or indirectly into the river Ganga without subjecting the trade effluents to a permanent process by setting up primary treatment
In the very recent case of T.N. Godavarman Thirumulpad v. Union of India, that raised the issue of conservation of forests, Justice Y.K. Sabharwal, held, “Considering the compulsions of the States and the depletion of forest, legislative measures have shifted the responsibility from States to the Centre. Moreover, any threat to the ecology can lead to violation of the right of enjoyment of healthy life guaranteed under Art 21, which is required to be protected. The Constitution enjoins upon this Court a duty to protect the environment.”
Article 246 of the Constitution divides the areas of law between the Union and the Member States. The Union List (List I) includes defence, foreign affairs, nuclear energy, transportation intestate, shipping, air trafficking, oil fields, mines and rivers between states. The State List (List II) covers public health and sanitation, agriculture, supply of water, irrigation and drainage, fisheries. 
The list (List III) (which allows both the State and the Union to legislate) includes forests, wildlife protection, mines and minerals and development not covered by the Union list, population control and factories. From an environmental point of view, the allocation of legislative authority is important–some environmental problems, such as sanitation and waste disposal, are best dealt with at local level; others, such as water pollution and the protection of wildlife, are better regulated by uniform national legislation.
Article 253 of the Constitution empowers Parliament to make laws that fulfil India's international obligations and any decisions taken at an international conference, association or other body.
Notwithstanding anything in the foregoing provision provisions of this chapter, Parliament has power to make any law for the whole or any part of the territory of India for implementing any treaty, agreement or convention with any other country or countries or any decision made at any international conference, association or other body. 
In 1980, the Tiwari Committee recommended the introduction of a new entry on "environmental protection "in the concurrent list to enable the center to legislate on environmental issues, as there was no direst entry in the seventh, allowing Parliament to adopt comprehensive environmental legislation. However, the recommendation had to consider the power of Parliament under Art.253.
ART. 14 states, “The states shall not deny to any person equality before the law or the equal protection of the laws within the territory of India.’’ 
The right to equality can also be infringed by decisions taken by the government that affect the environment. An arbitrary action must involve the denial of equality, so that urban environmental groups often resort to Art.14 quashing arbitrary municipal building permits contrary to development rules.
Article 21: Right to Wholesome Environment
"No person shall be deprived of his life or personal liberty except according procedure established by law."
In Maneka Gandhi v Union of India, the Supreme Court, while clarifying the importance of the' right to life' under Art. 21, held that the right to life is not limited to mere animal existence but extends to the right to live with basic human dignity.
Likewise, while interpreting Art. 21 in the Ganga Pollution Case, as discussed earlier, Justice Singh justified the closure of pollutants.
Justice Singh justified the closure of polluting tanneries observed: "we are conscious that closure of tanneries may bring unemployment, loss of revenue, but life. Health and ecology have greater importance to the people."
 The Constitution 42nd Amendment Act and the Environment, 1976.
 INDIA CONST Art. 48A and Art.51 (A)(g).
 INDIA CONST Art. 51(A) (g).
 Supra note 1.
 http://www.legalservicesindia.com/article/1926/Environmental-Laws-and-Constitutional-Provisions-In-India.html .
 L.K. Koolwal vs State Of Rajasthan And Ors. AIR 1988 Raj 2, 1987 (1) WLN 134.
 M.C. Mehta v. Kamal Nath & Ors., AIR 2002 SC 1515.
 Supra note 7.
 T.N. Godavarman Thirumulpad v. Union of India, AIR 2005 SC 4256.
 INDIA CONSTI. Art. 246.
 Supra note 5.
 Supra note 12.
 INDIA CONSTI. Art. 253.
 INDIA CONSTI. Art. 14 and Art. 19 (1) (g)
 Supra note 5.
 Maneka Gandhi vs Union Of India, AIR 597, 1978 SCR (2) 621
 M.C. Mehta Vs. Union of India (Uoi) and ors. AIR 1988 SC1037.