I wouldn't rule them out on that ground alone.
Many law firms are wary of someone who seems to have moved around a lot. Some will not touch them.
But it is worth finding out more. You could just find a star that others have overlooked.
No manager wants to hire someone who is going to turn around and quit after a year on the job. But how can you tell if a candidate is going to stick around, especially if he has a history of job hopping?