Narrative:

Left early morning from XXX to fly to YYY to pick up an aircraft part. YYY is an uncontrolled private field. Departed YYY for XXX, VFR GPS direct to XXX. Did not talk or call flight service or ATC. Altitude 2000 ft. Radio monitored 122.8 and 123.0. As I approached WWW, WWW approach control came on frequency 122.8 stating aircraft west of ZZZ come up on frequency 118.2. I came up 118.2 and called approach control, they told me a state of emergency existed and I was to land immediately. I said I was on the way to XXX, could I land there, he said 'no,' land at ZZZ. I complied with the instructions, landed at ZZZ and received landing clearance from ZZZ tower. Immediately upon landing, law enforcement personnel and tower personnel made copies of my license. I was informed a national emergency situation existed and all aircraft were grounded. I followed instructions and don't believe I did anything wrong.

Google
 

Original NASA ASRS Text

Title: WHEN MONITORING APCH FREQ, APCH CHALLENGES VFR ENRTE PLT TO LAND AT ZZZ DUE TO NATIONAL EMER NOTAM.

Narrative: LEFT EARLY MORNING FROM XXX TO FLY TO YYY TO PICK UP AN ACFT PART. YYY IS AN UNCONTROLLED PRIVATE FIELD. DEPARTED YYY FOR XXX, VFR GPS DIRECT TO XXX. DID NOT TALK OR CALL FLT SERVICE OR ATC. ALTITUDE 2000 FT. RADIO MONITORED 122.8 AND 123.0. AS I APCHED WWW, WWW APCH CTL CAME ON FREQ 122.8 STATING ACFT W OF ZZZ COME UP ON FREQ 118.2. I CAME UP 118.2 AND CALLED APCH CTL, THEY TOLD ME A STATE OF EMERGENCY EXISTED AND I WAS TO LAND IMMEDIATELY. I SAID I WAS ON THE WAY TO XXX, COULD I LAND THERE, HE SAID 'NO,' LAND AT ZZZ. I COMPLIED WITH THE INSTRUCTIONS, LANDED AT ZZZ AND RECEIVED LNDG CLRNC FROM ZZZ TWR. IMMEDIATELY UPON LNDG, LAW ENFORCEMENT PERSONNEL AND TWR PERSONNEL MADE COPIES OF MY LICENSE. I WAS INFORMED A NATIONAL EMERGENCY SIT EXISTED AND ALL ACFT WERE GNDED. I FOLLOWED INSTRUCTIONS AND DON'T BELIEVE I DID ANYTHING WRONG.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.