Former Chief Justice Reynato Puno said on Thursday it would be unlikely to pass the proposed Bangsamoro Basic Law under the 1987 Constitution.

In a press briefing in Malacanang, Puno said federalism should come first before the BBL could materialize.

"I’m saying that it will be very difficult for this bill to overcome a constitutional challenge before the Supreme Court because precisely, we have a unitary government that is not empowered to grant these identity-based demands of our Muslim brothers," he said.

"These identity-based demands can be granted only in a federal form of government," the former chief magistrate said.

He recalled what happened to the Memorandum of Agreement on Ancestral Domain, which the Arroyo government pushed to address rebellion of the Moro Islamic Liberation Front in Mindanao, and the proposed BBL under the Aquino administration.

The Supreme Court declared the MOA-AD as unconstitutional in 2007. The bill on Bangsamoro during the Aquino government did not get support from Congress.

President Rodrigo Duterte has expressed his commitment to pass the Bangsamoro bill under his government.

Puno, an advocate of federalism, blamed the Marawi crisis on failure of the government to address the problem in Mindanao.

He said the "most urgent reason" why the Philippines should federalize is "to enable the country to deal with the demands of our Muslim brothers to have their own homeland, which they can govern according to their culture, religion, language and history.

"This aspiration of our Muslim brothers cannot be substantially granted unless we change our unitary government. This frustration of our Muslim brothers to establish a state of their own has threatened to wreck our Republic. Their cry for separation and independence has resulted in open rebellion and worse, they are now assisted by some foreign elements," he explained.

Puno noted that to date, Marawi has yet to be fully recovered by military from the Islamic State-inspired Maute terror group.

"You know, this demand of our Muslim brothers for self-determination, for self-rule is not of recent vintage. They have always tried to preserve their identity during the time of the Spaniards who colonized us for three centuries, and the time of the United States that colonized us for about half a century. All the efforts to absorb them have failed. Neither the subtle efforts to assimilate them succeed. There is only one way to deal with them and that is to respect their identity and to live with them under a cooperative form of a federal government," he added.

Puno indicated that if he would be offered to be a member of the 25-man consultative committee to draft federalism, he would accept. Celerina Monte/DMS