religion requires child sacrifice or it requires polygamy or anything else that is illegal and repugnant to society then they wont get to practice it
Human sacrifice, in whatever form, harms another human, and thus is quite illegal.
Polygamy? The act that's typically prosecuted in the US is when somebody marries multiple others without them knowing. The old sailor's "woman in every port". But what if all parties are consenting with full knowledge?
What about the "vision quests" some tribes practice by taking hallucinogenic substances? These are generally done in controlled situations, and do not lead to long disability or addiction.
We have, or at least had, laws against "unnatural sex". Even between a married, consenting couple in private. It may be "repugnant", but I feel that if I'm not offended at least a bit by what others do, society isn't free enough.
If it doesn't directly threaten or harm another, or break a contract, it shouldn't be illegal.
As for convict's rights, it is commonly held that, at least during their sentence, that they've forfeighted their rights. But what about once they get out? I can see a period of restriction, but I believe that regaining the right to keep and bear arms should be a scheduled part of that restoration.
If you look at career criminals, as a rule, they're unable to keep their noses out of trouble for any length of time. If somebody is convicted, serves their time in prison, is released, then stays out of trouble for, say, a decade, why shouldn't we restore their rights? A kid (I'm talking mental maturity), steals a car at 18. He serves five years in prison, learns to be a welder or some other trade. He's now 23. He finds a job, keeps up with his parole officer, eventually marries. Let's say that he's now 25. At 26 he has his first kid. At age 33 he has two kids, age 7 and 5.
Do you think this man, who stole a car as a 'kid', but has since kept his nose clean, deserves to legally own a gun, be able to teach his children firearms safety? When the one who hasn't kept his nose clean, obtained a gun illegally 9 3/4 years ago, and is serving a new 20 year sentence?