ISLAMABAD (AFP) - Politicians have been assassinated, European countries threatened with nuclear annihilation and students lynched, all in the name of combating blasphemy in Pakistan, where the legal punishment for insulting the Prophet Mohammed is death.

In the latest case, Pakistan's Supreme Court on Tuesday (Jan 29) upheld the acquittal of a Christian woman who spent years on death row after being convicted of blasphemy, dismissing a petition filed by Islamists who have called for her execution.

Few issues are as inflammatory in the conservative Islamic republic as blasphemy. Here's a brief history of where the law came from and how it has changed the country over the years.

Who made the law?

The country's first blasphemy law was originally passed down from Pakistan's former colonial masters and was largely aimed at keeping the peace between different religious communities on the subcontinent.

The framework was later given a boost during the rule of former hardline Islamist dictator Zia-ul-Haq in the mid-80s.

His military government passed a series of new statutes that included a provision for capital punishment in cases where the Prophet Muhammad was insulted.

However, to date no one has actually been executed for blasphemy, with most punishments commuted to life sentences. But mere accusations of insulting Islam have sparked mob lynchings and murders.

What have been the consequences?

International rights groups have long criticised the legislation as a tool of oppression and abuse, particularly against minorities.

In recent years, it has also been used to smear dissenters and even politicians.

The topic is so inflammatory that even calls to reform the law have provoked violence, most notably the assassination of Salmaan Taseer - the governor of Pakistan's most populous province - by his own bodyguard in 2011.

His murder was followed the same year by the killing of minority affairs minister Shahbaz Bhatti, a Catholic, who had also vowed to maintain his opposition to the laws in defiance of death threats.

The blasphemy issue has also created a new religious extremist movement that has dictated terms to successive governments and paralysed the country at will with violent protests.

In less than two years, the Tehreek-e-Labaik Pakistan party (TLP) - or the Movement at the Service of the Prophet - has become one of the most powerful groups in Pakistan.

Led by firebrand cleric Khadim Hussain Rizvi, the far-right religious party has weaponised the ultra-sensitive blasphemy issue in the Muslim-majority nation.

This has sparked fears the TLP is radicalising the country's heartland and opening a dangerous new chapter in Pakistan's brutal confrontation with extremism.

Its leaders have gone on to threaten to "wipe Holland off the face of the earth" with nuclear weapons, call for the assassination of Pakistan's top judges and mutiny in the military ranks.

What's next?

Activists have long demanded reform, saying the legislation is too often abused to settle personal scores and target religious minorities.

The law is so vaguely written that defining blasphemy can be difficult if not impossible and criticism of the law could be perceived as blasphemy itself.

Following the murders of Taseer and Bhatti, mainstream politicians have steered clear of renewing calls for reform of the blasphemy law, fearing violent reprisals.

The recent uptick in violence, along with prosecutions of alleged offenders, comes as Washington added Pakistan this month to a blacklist of countries it says wantonly violate religious freedom.

Islamabad later dismissed the US move as politically motivated.