The Supreme Court is hearing arguments in a suit brought by the President against a ruling coalition of Islamic parties in the North-West Frontier Province (NWFP) who voted in a law under which citizens will be forced to respect the call to prayer and observe Islamic prayer times. Businesses will be forced to close during prayers.
The law could not have come at a worse time for General Musharraf, the leader the US has called its principal ally in the "war on terror. It is coming into force just as it has emerged that two of the London suicide bombers spent time in Pakistan, and General Musharraf is confronting accusations his country has not done enough to curb Islamic militancy.
Under the new law, known as hasba in Pakistan, unrelated men and women will not be allowed to be seen in public together, and singing and dancing will be "discouraged". The media will also be subject to censorship to ensure "publications are useful for the promotion of Islamic values". All this will be enforced by a Muslim cleric, appointed to the position of mohtasib.
The law has been compared to the Department for the Promotion of Virtue and Prevention of Vice set up in Afghanistan under the Taliban. It had its own police, who forced women to wear the burqa and arrested men whose beards were not long enough.
General Musharraf has asked the Supreme Court to rule the new law unconstitutional, which would overturn it. "Islam calls for brotherhood, unity, well being and learning," he said. "Please do not believe those who support extremism. They want to push Pakistan backward."
Since partition from India, the debate has raged over whether Pakistan's identity is as a secular homeland for Muslims, or an explicitly Islamic state with Islamic laws.
General Musharraf is under pressure to make his own position on the question clear. Although he is seen as a secularist in the West, it is an embarrassment to him that the parties behind the new law have been his political allies at home, albeit informally.
Unable to forge any sort of pact with Pakistan's liberal, secular parties, who oppose him as a military dictator, President Musharraf has been forced to rely on an ad hoc alliance with the Islamists. Now that alliance has come back to haunt him.
The Muttahida Majlis-e-Amal (MMA), an alliance of religious parties that took power in NWFP in 2002 on a wave of resentment at the US-led war against the Taliban in Afghanistan, says it campaigned on a promise to bring in such a law.
Pashtun-dominated NWFP is highly conservative, and there probably is support for such a law there - many of the Taliban were educated in the madrassas of NWFP. But in the more liberal parts of Pakistan, particularly Punjab, it has caused an uproar.Reuse content