The high court ruling appeared to contradict an earlier decision by the country's Federal Court in 2014 that upheld the government ban following a legal challenge by the Roman Catholic Church, which had used the word Allah in its Malay-language newsletter.
"The court has now said the word Allah can be used by all Malaysians," Xavier said. "Today's decision entrenches the fundamental freedom of religious rights for non-Muslims in Malaysia" enshrined in the constitution, he added.
Muslims account for about two-thirds of Malaysia's 32 million people, with large ethnic Chinese and Indian minorities. Christians comprise about 10 per cent of the population.
Most Christians in Malaysia worship in English, Tamil or various Chinese dialects, and refer to God in those languages, but some Malay-speaking people on the island of Borneo have no other word for God but Allah.
Three other words — "kaabah" or Islam's holiest shrine in Mecca, "baitullah" or house of God, and "solat" or prayer, were also banned in the 1986 government directive.
The United Malays National Organisation and the conservative Islamic Party in joint statement said they viewed the court ruling with concern and demanded the government pursue the case in the Appeals Court. Home ministry officials couldn't be immediately reached for comment.
The government ban was introduced under the rule of an UMNO-led coalition, but the coalition was ousted in a historic 2018 elections. UMNO returned to govern under a new Malay-dominated government last year following a series of political manoeuvres.
Government counsel Shamsul Bolhassan was quoted by The Star newspaper as saying that the four words can be used in Christian materials according to the court's ruling, as long as it clearly states it is intended for Christians only and a symbol of a cross is displayed.
The ruling was a result of a long legal challenge by a Christian woman whose religious materials containing the word Allah were seized by authorities at the airport when she returned home from Indonesia in 2008.
The controversy over the usage of Allah has provoked violence in Malaysia. Anger over a lower court ruling against the government ban in 2009 led to a string of arson attacks and vandalism at churches and other places of worship. That ruling was subsequently overturned by higher courts.
-AP