Is there any kind of law against this...?

My stepmother hates me. She cooks dinner every Sunday - I try and get out of it as much as I can because she always messes next to my food. There is always a hair or a piece of dirt or something in my food. Is nearby any sort of legal action I can bring against her the next time she does this?
Sounds like "Personal" Harassment .....a lawyer will supply better advice...then take her beforehand "Judge Judy" before 4million people aught to put her in her place How nearly you ask her to stop? Be an adult and address the issue with out wasting tax dollars b/c you can not communicate next to your family.

She is a family member it seem you want revenge on your step mother more than the food tampering to stop.

I would suggest some family counseling to fix these underlying issues.
I'd think it be some sort of harassment if you can get evidance against her thats not as stupid as a hair within your dinner. tampering with food is a federal offence but you involve proof its intentional good luck
Have you tried discussion to both of your parents about this? I don't mean one at a time, but both of them together?

If I were contained by your position, I would sit them both down and ask her if there is some sort of issue between the two of you that you need to know about, as you keep hold of finding items (such as the hair and the dirt) in your food, and that since this is an ongoing matter it no longer seem like just an isolated "accident".

Get your Dad in on this, as it will effect him as all right. If there indeed is an ongoing pattern of harassment, next you'll need to make sure he's aware of it - because tampering is darned complex to prove (she can always claim she's just a lousy cook), and without actual intent to grounds injury or harm, either actual or psychological, then most police and courts won't consider it a criminal exploit.

So get your Dad involved, make sure to discuss it with the both of them together, and if this cannot be resolved that instrument then I'd suggest you look forward to eating on your own every Sunday.
Be glad she cooks for you. She probably also cleans up after you. A little hair, or anything else, in your food helps build up your immune system. Just verbs the hair out and be glad you have something to eat. Think of adjectives the homeless people in this country that have to scrounge surrounded by dumpsters and trash cans for food. They'd love to have your meal. Deal next to it! Grow up...Have you ever heard the adage "Don't bite the hand that feeds you"? Get a position, move out and feed yourself you ungrateful wretch! She's probably as tired of your incessant whining as you are of her cooking. It could be worse.
Don't eat the food, or cook your own food. No being dirty surrounded by the kitchen is not a crime.
Just be glad you have a mother that will cook at all, in the military we knowledgeable to pick out insects and bugs before eating. get use to it. Probably not...I suggest you'd need to prove it and that would be difficult and costly. I would stay away from her, she sounds like bad word.
Gather and collect proof. Take photos and keep a log respectively time it happens. Once you have evidence and can show a pattern of mishandle, take it to the police or your state or county social services agency for children and let them decide if it is swearing. It could be a case of you being mad at your step mom. Filing a myth and accusations of abuse is also illegal.There are other two sides to a story. Talk to your step mom and tell her how you feel. Or talk to your Dad going on for it.