Another scenario, for example, could people that live in California and use certain drugs that are legal in the State, but illegal under Federal law, be arrested in other jurisdictions for those past deeds if anti-drug advocacy groups in California denounce the person?
No need for that person to travel. Feds could arrest, charge, convict and incarcerate right in CA now. Federal law trumps state law, so the feds, if they decided to, could go to CA, WA, CO, etc and prosecute all the MJ growers, retailers and customers. They have jurisdiction.
Now, if it were, say, Idaho trying to charge someone from Washington State with MJ related crimes for being involved in MJ only while they were in WA, that would probably not pass muster.
However consider that the feds will charge people who have sex with minors while overseas even if it's legal in the country they were visiting, and you have potential precedent to charge under state drug laws too.