Since independence, the Supreme court and the lower courts many times acts like activists and force the authority to take action on something and sometimes directing the Government regarding its policies and administration. This is termed as Judicial Activism.
It has played a very active role in dispensing justice with cases like A K Gopalan vs State of Madras case (1950) followed by the Shankari Prasad case, etc. However, the judiciary remained submissive until the 1960s but its authoritativeness started in 1973 when Allahabad High Court rejected the candidature of Indira Gandhi. This has evolved in great extent after the commencement of public interest litigation(PIL) by Justice V.R Krishna lyer in the Indian Judicial system.
Golaknath Case: In this case Supreme Court decided that Fundamental rights enshrined in the part 3 of the Constitution are not amendable.
Keshavananda Bharati Case: In here Supreme Court introduced the doctrine of basic structure i.e. Parliament has the power to amend the Fundamental rights without altering the basic structure of the Constitution.
Similarly Supreme Court has assumed a supervisory role in the investigation done by CBI in 2G spectrum case.
Bombay High Court order to cut Jolly LLb2: After few lawyers approached the court that some scenes in the film showed them in the bad light. The court passed the judgement in their favour. This is one of the cases where courts have taken up the work of another exclusive authority.
Striking down the NJAC Act: The National Judicial appointment commission (NJAC) was proposed by the body which have the power to appoint judges to the high courts and Supreme Court. Though passed by both the houses of the parliament it was termed as unconstitutional by the Constitutional Bench of the apex court and at last repealed.
Firstly, it is mainly said that in the name of activism, personal opinions were attached.
Secondly, the theory of separation of power is displaced by activism. However, its significance lies with position given to the institution as a place of hope for aggrieved man.
The role of judges should be scrupulously limited; their job is merely to say what the law is, leaving the business of law-making where it property belongs, that is with the legislators and executives.
While delivering a judgement in December 2007, the Supreme Court of India called for Judicial Restraint and asked courts not to take over the functions of the legislature or the executive, saying there is a broad separation of powers under the constitution and each organ of the state must have respect for others and should not encroach in other organs.
The thing if a law made that violates the provisions of the Constitution, it must be struck down, if required interfere in the other domain (legislature and executive). And as to what I think judicial review and judicial activism are much like a same with little difference. Review is to decide if the law is consistent with the constitution. On the other hand Activism is the behavioural concept of the concerned judge. It is primarily based on public interest, speedy disposal of cases, legal aid, etc.
When a question of fundamental right comes, court act as a custodian with the power of judicial review (article 31B of the Constitution) making it the basic structure of the constitution (as in 2007 SC has given a judgement that judicial review is a basic feature of the constitution and it could not be taken away by putting a law under the 9th schedule) and the power of activism is as implied.