Yep, that's what he said: "I could arrest you." Places and situation changed to protect the guilty.

Client called me Saturday afternoon. Said, "My car was broken into. Can you help me get my stuff back?"
Not normally what I do, but hey - it's Saturday afternoon on Memorial Day weekend. What else am I going to do? "Sure, I'll do what I can," I said.
I set up a few tricks involving Craigslist and ebay, something to send me an alert when certain criteria were met. Within an hour, I had a perfect match for my client's iPad. "Do you want me to set up a buy?" I asked.
"Yes," Client said.
Here's where it started to go south. I called the Flarksville Police Department to let them know what I was up to. No answer, Memorial Day weekend you know. I called my lawyer to make sure what I was about to do was - at the very least - not illegal, if not outright stupid. "I don't see a problem," Lawyer said.
Off we went. South to the fictional town of Flarksville. Twice I tried to raise the good people at Flarksville's Finest, to no avail. Memorial Day weekend, you know.
I met the suspect in a well-lit parking lot at the intersection of XXXst Boulevard and Ft. XXXXXX Drive in the fictional town of Flarksville.
All tall and tattooed, Mr. Thug got out of his SUV and walked a brand new iPad over to my car. I climbed out into the sweltering heat of late May and shook Mr. Thug's large hand.
"Dude, man - this shit is tight," he said.
"Cool," I said. "My nephew is home from the sandbox tomorrow. Thought this might be a nice welcome home gift."
"Shit, dawg, he gon love this. Man, dude - I'm tellin you, this shit is tight," Mr. Thug said.
I still wasn't clear on exactly what that means, this shit is tight, but it seemed to suggest a ringing endorsement of the merchandise.
After a few minutes of niceties, during which I videotaped Mr. Thug's face, arms (clear shot of tattoos), girlfriend, and license plate, we got down to business. "How much?" I asked.
"Shit, dude, man this is brand new. This shit is tight. This shit sell for $800 retail," Mr. Thug said.
"I'm assuming we're going to be dealing at wholesale prices," I said.
"Awwww yeah, dude. Man, we doin business," Mr. Thug said. "I'm gon let you have this shit for $400, half price."
Well, of course I couldn't pass a deal like that up. Especially considering the fact that the serial number was an exact match for the iPad my client purchased at full retail just last week.
Man - dude, this shit IS tight.
I peeled off four benjamins and pressed them into his huge open palm, all on video. I was strolling back to my car when an idea hit me. Turning, I asked, "Say, would you mind making out a bill of sale on this? You know, just so we have a record."
"Naw dude, that ain't a problem," Mr. Thug said. "You got some paper?"
I handed him a sheet of paper from my surveillance field book and he dubtifully penned the following bill of sale:
I, XXXXX XXXXXXX, herby [sic] sell this ipad to XXXX XXXXXXXX for $400. May 28, 2011.
There are two totally astonishing things about this particular bill of sale. First, Mr. Thug used his real name. Second, he signed it.
Late now, I thought it might be advantageous to see if anyone at the Flarksville PD was around to answer a call. To my utter suprise, a dispatcher picked up on the first ring.
I told her the whole story. "I'll send a patrol car right over," she said.
"Thanks," I said.
Roughly 30 minutes later a young street cop rolled up, exited his vehicle, and approached. I offered a hand in greeting.
"I don't shake," he said. "What's the story here?"
After about 10 mintues of Street Cop berating my client for not adheering to "OpSec" protocol, I asked if it might be possible to speak to his superior. This made Street Cop very happy.
Superior rolled up 20 minutes later, exited his vehicle, and huddled with Street Cop, whispering authoratatively.
Superior was about five foot six, bald head, tighlty trimmed mustache, and glasses. He walked with his chest out, ready for a confrontation. After about five minutes of briefing and debriefing, Superior called me over.
"Son, I need you to come over here," he said, pointing to a specific spot. I approached, respectfully, if a little tired. As I neared the indicated spot, Superior jumped backward, hand on weapon.
"Son, you need to stop right there," he said. "I don't want you anywhere near my weapon." He gathered up my PI License, my drivers license, and my handgun permit. "Check him out," he said to Street Cop, who dutifully hopped into his cruiser and ran my information.
"Son," he asked in a sarcastic yet authoritative tone, "do you have any law enforcement experience?"
"No sir," I said
"Well," he said, "I could tell. What you've done here is putting me in a bad position, son."
"Sir, may I ask a favor of you, please?" I asked. And before he had a chance to reply, I said, "I am not your son. Please call me Mr. XXXXXXX or some other courteous name, but don't call me son again."
"You," he said, all red in the face, dome a-gleaming, "DO NOT tell me what to do. I could arrest you for possession of stolen goods. You've just ruined any chance that this ALLEGED thief is ever going to be held accountable for his actions.
"We have PROCEDURES that must be followed," he ranted, on a roll now. "You can't just come in here and buy stolen goods. That's a crime.
"I could have you arrested," he veritably yelled.
* * *
Six months later, Mr. Thug pleaded gulity. He was sentenced to six years in prison. Smash and grab theft went to near ZERO after Mr. Thug was arrested (May 29, 2011 - the day after I was told that I could be arrested for possession of stolen goods.). It seems that verified video, fingerprints, a signed and dated bill of sale, and old fashioned detective work actually is admissible in court. And furthermore, Mr. Superior, it is not a crime to gather and return stolen property to its rightful owner. I haven't seen Street Cop since, but really hope to meet him somewhere and shake his hand. Or at least try.
"I don't shake." Really?