Whitetail72,
I also own land and I know how frustrating it can be to have someone abusing it. It would be ideal to find out who it is and then have the police deal with the issue. But, most times a person just has to wait till the perpetrator either matures, moves away, learns to respect others rights or loses interest. As there are laws against setting "booby traps," I would not place spike strips or any other object that may cause someone to get hurt.
I can see it now: a person is joy riding on your land (without your permission) hits a spike strip and crashes. They are injured in the process and are now suing the deep pocket (that would be you the land owner). Land owner (that would be you) loses land to pay for legal bills. This is wrong, but this is the world we live in.
drox