Hounddog,
There is nothing wrong with digging anywhere on your own property. Unless you have items on your property that can legally have access through your property such as power lines underground, gas lines or others. The digging is not the wrong, it is when you find something of a historical or archeological value and you continue to dig without reporting it to the authorities. It is just like the underground power or gas lines, you must report when you have to dig near one of these. The county or state will send someone out to locate the pipeline so as you not being sued for damages. The same is true of artifacts. Once found and you continue to desecrate them without contacting the authorites. You can get by with it, but if a neighbor or anyone else finds out, you can be arrested. These laws are on the books. When unsure contact an attorney. If not you could be liable or go to jail. Also if there is enough artifacts on your property, when you are in violation you can be evicted from your property and the government will then own your property while you are on the street or in jail. The legal way is the best way.