I don't know that I'd use the word "discrimination" but it definitely sounds like harassment
You said your stepson was dating the daughter of the sheriff. Do you mean THE sheriff or a deputy? If it's a deputy, then by all means complain to his superior officers. If it is the sheriff, then it becomes a bit more complicated.
If there is another local law enfocement agency, such as city police, you could notify them of the issue in an effort to be proactive as to any future problems. Similarly, you could discuss the matter with the prosecuting attorney in your area.
You could also contact an attorney in the area. You'd be looking for an attorney that handles civil litigation
, especially regarding suits against law enforcement. Additionally, you may want to look for an attorney in a neighboring county. As you can imagine, an attorney in the county may not want to sue a local law enfocement agency.
As to searching your son or his car, law enforcement can only searh him or his car in limited circumstances. He could be searched if he is arrested or if there's reasonable suspicion of criminal activity. If he is simply stopped for a routine traffic violation, he can refuse to permit a search.
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