Final answer:
The interest group tactic used by the groups involved in the recent Michigan affirmative action cases is filing amicus curiae briefs.
Step-by-step explanation:
The interest group tactic used by the groups involved in the recent Michigan affirmative action cases is filing amicus curiae briefs. Amicus curiae briefs, also known as 'friend of the court' briefs, are filed by interest groups to provide their official positions on cases to the judges. These briefs aim to influence the court's decision by showing how the outcome will impact the interests of the group.