The right to privacy is the point. The can't ban contraceptives because that would violate both privacy and equal protection of the 14th Amendment.The government can however ban contraceptives as there is nothing in the Constitution preventing it.
The first case there is about right to privacy. The second case there is about equal protection. Neither one said that there is a right to contraceptives.
I thought that they are not allowed to keep people from arming themselves. The 2nd doesn't say anything about not legislating certain types of weapons, just that they can't legislate all weapons (guns).Actually the government is not supposed to make any laws regarding guns. They do it. But they're not supposed to.