There arent any federal or state laws making it illegal for you to not tell a partner about an STD you may have. Laws on the topic vary from state to state. That being said, it is typically illegal, civilly and criminally, to knowingly or recklessly transmit an STD.

Can you be charged for giving someone an STD?

Crimes Act 1900 (NSW) People can also face severe penalties under the Crimes Act 1900 where they transmit serious STIs. Where they do so recklessly, the maximum penalty is 10 years imprisonment.