Legal Question in Real Estate Law in Illinois

You can block the delivery. I think you are thinking about letting them on the driveway and then blocking it (with your car, I hope) until the police get there.

It would be legal because you have the right to detain people like a guard in a store can detain shoplifters.

Be prepared for the dumper not to be happy about this. You are not allowed to use violence. The amount of force available to a private individual is less than the amount allowed for police officers. Unless you are a very large person and can physically intimidate them I would recommend having someone with you who can act as a witness, a good idea under all circumstances, and taking down the license number and description for later arrest. Photos help too.

Even the police have legal problems when making arrests and they are trained and have some experience in the matter. This is not a task that I would encourage non-professionals to undertake. If you use too much force or are hurt yourself, you are pretty on your own.

Only if you can do so peaceably, which is probably unlikely. Better would be photos and/or videos, making sure you record the license plate number and get a good description of the dumpers. I am not sure why people cannot understand that those dumpsters are not free.

I agree with Tom. You would be better off taking pictures and obtaining the license plate number. It probably would not hurt if you also had a witness with you.