For those of us traveling across America to Las Vegas...
Thought I would post this for your information.
Feel free to add upadated information if your state has change their laws.
Law varies from state to state, but detectors are generally legal in private vehicles under the Communications Act of 1934 and illegal in commercial vehicles by DOT regulation (49 CFR 392.71). Exceptions:
Illegal in all vehicles: Virginia, Washington D.C., U.S. military bases
Illegal in commercial vehicles under state law: Illinois, New York, New Jersey (specifically, commercial vehicles over 10,000 pounds (4,500 kg) and all vehicles over 18,000 pounds (8,200 kg)) Also illegal in all commercial vehicles over 10000lbs under US federal law
Indirectly illegal (Illegal due to prohibitions against affixing items to windshield - "obstructing vision"): Minnesota, California, New York
Repealed: Connecticut (repealed in 1992)
Be safe out there!