"You don't change an institution with such a long history from one day to the next just to satisfy the whim of one group of people," he says. "Marriage is a relationship between a man and a woman intended to produce children. You can't get around that."
But he concedes there is no political support for reversing the law, even though the government is now led by the Christian Democrats, which had opposed the legislation.
Henk Krol, editor of the magazine Gay Krant, argues civil unions are an intermediate stage on the way to full marriage rights for gays, which he says are inevitable.
"A civil union is a second-rate marriage," he says. "People want a honeymoon. Not a trip to celebrate a registered partnership."
He says those who oppose gay marriage for religious reasons often soften their thinking when they realize they won't be forced to accept gay couples joining their church.
"It's an issue of separation of church and state," he says. "We don't have gay marriage here. We have civil marriage, and it's the same for everyone."
But Thus, who was raised Catholic, said the fact of her marriage itself has helped win over religious people.
"Especially for religious people, marriage makes a statement that 'this is someone I love and will grow old with'," she said.
"When you're just 'partners' or 'living together' they think ... you know, every day a new lover'. With marriage, the commitment is real, and they believe it."
