There are still laws making it illegal to have gay sex on the books in parts of the US, they just aren't usually being enforced. They could start enforcing them any time they want. They're not constitutional, but that hasn't stopped states from doing lots of other unconstitutional things while people sued to block them. Once those suits go to the supreme court, the modern set of judges might validate those laws.

https://en.wikipedia.org/wiki/Sodomy_laws_in_the_United_Stat...

In some cases these laws also criminalize some forms of heterosexual intercourse, as a fun little example of how discriminatory laws targeting the minority can often be repurposed to punish members of the majority who step out of line.