If you want to pursue a career in law, wouldn’t you want to take law classes to test the waters? From my experience as a current high school/college runner, it might not be necessary to have a strength training class blocked out in addition to the sport. Stay focused on your training, use track as a motivation to know that something less boring comes after law class, and I think you should be fine.
From an admissions standpoint, I think you should also consider how much track weighs on your application. Unless you think that the strength training class will make you a significantly better athlete/candidate for recruiting, etc., you might want to consider another class. From my experience, doing strength training classes didn’t help as much, and you should have a training plan over the summer/pre-season anyways.
My coach always emphasized that hard work was the reward. If I were in your shoes and interested in law, I might take that class, knowing that I had a chance to work hard – and do what I love – on the track afterwards.