A warning to all my wacky stoned readers:

People primarily ask about the legal risks of past use because they want to be able to talk or write about their experiences. When describing past illegal acts, mentioning specifics about timing and location increases risk of prosecution. If the statute of limitations has not run out, it is possible that a judge could grant a search warrant?or in extreme cases, an arrest warrant?based on specific details of past use. In some areas, a positive drug test is treated as evidence of a crime.

[…]

Violations that have happened within the statute-limited period can be prosecuted if there is enough evidence. Simply talking about past use, by itself, is very unlikely to be considered proof of a crime, which means the authorities would need to have additional evidence to prove their case (or even get an arrest warrant). It is important to note, however, that out-of-court documented admissions of law violations can be strong evidence if a trial does take place.

[…]

Suggestion or evidence of past illegal substance use could pose a problem even if there is not enough evidence to support criminal charges. A few scenarios where this could be an issue are: in a fight for custody of children, if a parent?s past use is brought to the attention of child protective services, and in the workplace, where the mere suggestion of drug use could lead to the loss of one?s job or professional license.

Full Story: Ask Erowid: Is Past Substance Use Illegal?