Christianity has clashed with government over marriage before. According to Christian legend there was a priest named Valentinus who married couples against the wishes of government, we call him Valentine. According to legend, in the 1st century AD it is said that Valentine, who was a priest, defied the order of the emperor Claudius banning marriage by secretly marrying couples. The legend claims that soldiers were sparse at this time empire was at war. By banning marriage the emperor hoped to gain more soldiers by inscription. Another legend is that Valentine refused to sacrifice to pagan gods. Being imprisoned for this, Valentine gave his testimony in prison and through his prayers healed the jailer's daughter who was suffering from blindness. The daughter and Valentine became rather fond of one another and on the day of his execution (February 14th) he left her a note declaring his love and thanking her for her companionship that was signed “Your Valentine.” As a result, love letters between lovers during this time were often signed, "Your Valentine", to hide the couple's identities. The church declared February 14th the Feast Day of St. Valentine. This is the origin of our St. Valentine's Day traditions.
As a result of these legends surrounding St. Valentine, St. Valentine's Day has evolved into a day to celebrate love, marriage, and lovers.
If the legends hold any weight, it would appear that this priest did somehow challenge the Roman imperial government with regards to the right for couples to be married without government regulation or interference. Marrying lovers privately may have ultimately cost an early Christian priest his life.
At any rate, the legend at least causes us to pause and consider... who really is in charge of marriage anyways? God or Caesar? Christ said,
“Render to Caesar the things that are Caesar's, and to God the things that are God's.” (Mark 12:17, ESV)
Many use this argument to support turning to government for permission to marry. But is "marriage" Caesar's institution or God's? Are we failing to render unto God something that is God's?