"I can only recommend to all to have the courage to stand up effectively against this Islamisation that is creeping through Europe and represents a totally different culture," Governor Joerg Haider was quoted as saying by Reuters.
"We are really the pioneers on this," added Haider, also the leader of the far-right Alliance for the Future of Austria party.
The law requires plans for any building of "extraordinary architecture or size" to be approved by a commission to judge its compatibility with the standard look of towns.
This means that mosques would stand little chance of permits.
Haider make international headlines in the 1990s with xenophobic remarks when his rightist Freedom Party became the second biggest in Austria.
After an internecine power struggle, he broke away from the Freedom Party and founded the Alliance in 2005.
But the new party's national impact has been negligible since Haider decided to focus on his home region of Carinthia.
The new law drew immediate rebuke from the opposition and Muslims alike.
"We are creating a law for something that doesn't exist," fumed provincial Social Democratic leader Gaby Schaunig.
Schaunig said there was no request to build a mosque in the overwhelmingly Roman Catholic province.
Carinthia is home to 11,000 Muslims out of an estimated 400,000 population, the second-lowest Muslim population in Austria.
Muslims, estimated at 400,000 or nearly 4 percent of the population, also denounced the law.
Omar Al-Rawi, the spokesman for Austria's Islamic community, said it violated principles of equality and religious freedom and put
Austria's reputation on the line.
Though Islam is the continent's second religion, European Muslims are facing campaigns from far-right groups have stately mosques on claims that they are signs of the "Islamization" of Europe.
In Germany, a plan by the Turkish Islamic Union (DITIB) to build a mosque in Cologne has met opposition on claims that it would be too big for a city housing one of the most imposing Gothic cathedrals in the Christian world.
In London, a petition against a mosque next to the 2012 London Olympics site was posted on Prime Minister Gordon Brown's Web site.
In France, which is home to Europe's largest Muslim minority of about six million, the National Republican Movement (MNR) won two court cases last year against giving pieces of land at low prices to Muslims to build two mosques in suburbs of Montreuil and in Marseille, both having a sizable Muslim minority.
In Switzerland, two right-wing parties have launched a petition for a referendum to ban mosque minarets.
Source: Islam Online (English)
See also: Austria: Law proposal against 'unusual buildings'