The first article of Malta’s constitution proclaims “respect for the fundamental rights and freedoms of the individual”. The second makes Roman Catholicism the state religion....
In a nutshell this concordat says that the Catholic Church sets the rules for marriage and that the state agrees. Even so, in accordance with Article 4.2 marriage partners must sign away their right to get the divorce that in Malta doesn't even exist! Presumably that's to bind people if civil divorce is ever introduced, or if they're thinking of getting divorced abroad.