Well it depends a lot on your jurisdiction. In the start of Georgia, oral sex is illegal.
While in many places the production of pornography is illegal because it involves paying people to have sex.
Some places have laws related to sexual violence, in Australia porn that depicts non consensual sex is illegal (even if the people in the movie consent, they can't represent non-consensual sex. Also they can't pretend to be under the age of 18).
In the UK sexual acts of mutilation (example, fish hooks through the genitals) is illegal, even if consensual.
In California, under work safety rules, sexual acts in porn films must involve condoms.
The answer is complicated, basically in the US, it will depend on local state laws