Should both partners be Buddhist in a marriage? If they want get a love marriage can they still get married if one of the partners is not Buddhist. What is the law in Buddhism about marriage?
There is no such as a Buddhist law on marriage. If you like to have a long time partner its always good to have the same tendencies as he/she but such is not merely up to religion. Virtue, generosity, gratitude... all this things are not limited to a certain religion. So to seek for a partner with equal virtue or virtues one likes to follow, is quite good.
And there is no such as any cultural, national, or what ever discrimination. Of course such plays, even so, always a rule in live and society as much traditions have also to do with common virtues. The world is not full of Arahants and Noble Ones.
(thoughts come up sometimes ...and now they like to be great yogis ... :-) "I wan it all", but not to speak about those who even do not take on the responsibility of partnership)
There is no strict law about Buddhist marriage.
However, the Buddha did teach it is best (preferable) to marry a person of the same faith (religion). The Buddha listed the same faith (religion) as the 1st and therefore most important quality because it is your faith (religion) that defines your life values & morals.
For example, if you are a Buddhist, you will have the tolerance & loving-kindness to marry a person of another religion. However, if you are a Muslim, you will not tolerate marrying a person of another religion & ask them to convert to Islam (since Islam forbids interfaith marriage).
Please refer to the Samajivina Sutta.
Then the Blessed One spoke thus: “If householders, both wife and husband wish to be in one another’s sight so long as this life lasts and in the future life as well, they should have the same faith, the same virtue, the same generosity, the same wisdom; then they will be in one another’s sight so long as this life lasts and in the future life as well.”
When both are faithful and bountiful, self-restrained, of righteous living, They come together as husband and wife Full of love for each other.
Many blessings come their way, They dwell together in happiness, Their enemies are left dejected, When both are equal in virtue.
Having lived by Dhamma in this world, The same in virtue and observance, They rejoice after death in the deva-world, Enjoying abundant happiness.