Just days after Aaron Hernandez's death, his legal team has already filed a motion to have his murder conviction officially dismissed ... as part of a Massachusetts law that everyone's talking about.

As we previously reported, Hernandez's team believes that a concept called abatement ab initio requires the court to throw out Hernandez's conviction in the Odin Lloyd case because Aaron died before he could finish the appeal process.

Hernandez's legal team, led by Jose Baez, has now filed to make that happen -- but it won't come without opposition.

The Bristol County D.A.'s office tells TMZ Sports, "We have been reviewing the matter and intend to file an opposition to the defense motion within the next week."