According to new legal docs, obtained by TMZ, the actor's lawyers put Santa Fe sheriff Adan Mendoza and special prosecutor Kari Morrissey on notice ... instructing them to save all relevant info related to his now-dismissed manslaughter trial.

In a pair of preservation notices fired off this week, Alec's legal team told the prosecutor and sheriff to hold onto any emails, text messages, hard drives, documents, records and materials related to the investigation and prosecutions connected with Halyna Hutchins' shooting death.

On its face, it certainly looks like Alec is preparing to sue over his involuntary manslaughter trial, which came to an abrupt and shocking end last Friday when the judge dismissed the case after finding law enforcement concealed evidence preventing Alec from preparing his defense.

Remember ... Alec's attorney, Alex Spiro, claimed authorities intentionally concealed evidence of live ammo on the movie set ... a critical part of the case that could have helped Baldwin argue those around him were responsible for loose safety standards.

The judge dismissed the prosecution's case with prejudice, so it cannot be tried again.

Now, Alec's legal team is requesting all communications between the sheriff, district attorney and prosecutor related to the "Rust" shooting ... as well as documents, comms and info referencing or relating to Baldwin.

Alec walked out of court last week a free man ... and now it seems he's out for some legal revenge.

Worth noting, Baldwin might have an uphill climb to win a lawsuit against the special prosecutor ... he'd have to show prosecutors knew their case was weak, and concealed evidence to make it appear stronger