Tens of thousands of protesters against same-sex marriage in France marched in Paris on Sunday afternoon.
It is the first big rally since the law was signed by President Francois Hollande on 18 May. French people are bitterly divided over the issue.
Fifty protesters were arrested on Saturday evening for blocking the Champs-Elysees.
Police said 150,000 protesters are taking part in the march, but the organisers said the number is closer to one million.
The BBC reports they arrived in columns from a number of points around the city to the Invalides complex.
UMP member of parliament Jacques Myard told BBC News that the law had been passed by the governing party "by force" and his party would review it if re-elected.
Mr Myard said there was a "huge gap between this government and the citizens" over the marriage issue.
"This is something we cannot accept because of the fate of the children," he said.
"Those people are playing God, because they want to marry, but it won't stop at this stage. Then they will adopt, and then we will have children in families where there is no father or no mother."
A group of protesters chained themselves to metal barriers in the middle of the Champs-Elysees on Saturday evening.
Some released smoke bombs before police moved in and arrested them. Nobody was hurt.
A BBC correspondent said opposition to gay marriage has become conflated with all sorts of other anti-government grievances and the atmosphere in the country is particularly volatile.