Reynolds v US
This case refers to the first amendment, specifically the freedom of religion.
The issue before the court is that the law banning polygamy, The Morrill Act, is unconstitutional.
It states that the practice of polygamy is just as worthy of charges as the practice of human sacrifice, even under supposed religious protection.
This case holds modern relevance and is applicable now because without it, polygamy would still be practiced in Utah and Mormons would still be exercising their right to multiple wives. Because of this case, it was made sure that no one would ever have the right to more than one wife.
While it has not yet been addressed by the court, many believe the next step, after the legalization of gay marriage, in marriage equality is the legalization of polygamy. Though, in the eyes of the court, polygamy is still banned, and those who participate will be charged with bigamy.