The only way I can think of for US law to be relevant is if you want to record an international phone conversation etc.
Whether you’re part of the conversation or not, if you don’t obtain
consent, you need to have a reason to make the recording e.g. protection
of your rights, public interest, etc. Even if you have a legitimate
reason to make the recording, you can’t use that as an excuse to expose
irrelevant details of people’s private lives.
In the Criminal Code, it’s Chapter 28 (Art. 315 to 319). The Personal Information Protection Act may also apply.
Consent is required in some situations, e.g. the Regulations of Court
Audience and Regulations of Audio Recording in Court both prohibit
recording a trial without permission, even when it’s open to the public.
In USA, some states say no; but many states say “as long as you are knowingly part of the conversation” [eg, even if you don’t talk, you are at least ‘expected’ to hear this info as opposed to eavesdropping.]