I've gone back to school to get a crim justice degree so I can work in LE.
I'm 35.
A lot of the glamorous federal agencies, SWAT, etc, aren't interested in older applicants, according to their guidelines. However, if you make an effort to be fit and capitalize on your strengths, you'll find many are willing to at least talk about bending the rules to let you apply.
What I'm finding is that if you show an aptitude for the job you want, have an active willingness to build your skillsets, and are not the average person of your age, you will have a very good chance at doing what you might like to do in LE.
Granted, you may not get a position in the Secret Service because of your age, but as mentioned, many are hurting for good applicants just like every other job out there.