This is an often asked question: "In what states in the US are radar detectors legal?" First though radar detectors are currently illegal in the following states:

Virginia (VA)
Washington DC (DC)

Also, radar detectors are illegal to use at the federal level (in all states), in commercial vehicles over 10,000 lbs and on military bases, so keep that in mind.

Ok, here is a list by state where radar detectors are currently 100% legal to own and use:

ALABAMA (AL)
ALASKA (AK)
ARIZONA (AZ)
ARKANSAS (AR)
CALIFORNIA (CA)
COLORADO (CO)
CONNECTICUT (CT)
DELAWARE (DE)
FLORIDA (FL)
GEORGIA (GA)
HAWAII (HI)
IDAHO (ID)
ILLINOIS (IL)
INDIANA (IN)
IOWA (IA)
KANSAS ( KS)
KENTUCKY (KY)
LOUISIANA (LA)
MAINE (ME)
MARYLAND (MD)
MASSACHUSETTS (MA)
MICHIGAN (MI)
MINNESOTA (MN)
MISSISSIPPI (MS)
MISSOURI (MO)
MONTANA (MT)
NEBRASKA (NE)
NEVADA (NV)
NEW HAMPSHIRE (NH)
NEW JERSEY (NJ)
NEW MEXICO (NM)
NEW YORK (NY)
NORTH CAROLINA (NC)
NORTH DAKOTA (ND)
OHIO (OH)
OKLAHOMA (OK)
OREGON (OR)
PENNSYLVANIA (PA)
RHODE ISLAND (RI)
SOUTH CAROLINA (SC)
SOUTH DAKOTA (SD)
TENNESSEE (TN)
TEXAS (TX)
UTAH (UT)
VERMONT (VT)
WASHINGTON (WA)
WEST VIRGINIA (WV)
WISCONSIN (WI)
WYOMING (WY)