This happened today 29/03/2010
I was stopped by 5 police officers as I was smoking outside a ramen shop. An older police officer asked me if I had eaten ramen, I simply ignored him and gave him a blank stare. A female officer then requested that I show my passport. I gave her my gaijin card, and she read out that I was from England. The older officer tugged my bag and wanted to search it. I did not like being surrounded by police, and asked him if he had a search warrant in Japanese.
This stunned him and he replied by asking how I knew such a word. I did not move and he tried too reach for my bag. I told him again that he needed a search warrant. The officer then went behind me and pulled off my bag, and started to empty it's contents. They found some incense that I had purchased and rolling papers.
This is when the real problems started. I was taken to the small koban and they removed my jacket, hoody and also tried to take off my t-shirt (in public view). I stopped them from taking off my t-shirt. They took me to a room inside the koban and had me remove my belt, which the same old officer would not let me have back. I then was told to sit as they went through my belongings. He accused me of taking drugs, I said that I had done no such thing! A female officer (Nakajima Yuka) then told me to remove my shoes and socks, which I did.
After, they drove me to the big police station in Shibuya for interrogation and drug testing. A small detective dressed in black sat me down and tested the incense. Surely enough, it came out as negative. They then asked why I was carrying rolling papers, I said I like to smoke roll up cigarettes if I run out of tobacco at home. They then made me sign (fingerprint) numerous forms giving them permission to take the incense and also a urine test. The forms were voluntary, so I asked them what would happen if I refused to give my urine sample. Another detective (sorry for not taking names, there were 8 police officers in the room at the time) told me I would be taken to the hospital where a very painful procedure would be performed to take the urine by force.
I gave the sample, as I had finished, they brought in an officer who was bald (as am I) and said 'He is your brother!'. I did not find it amusing, I really wanted to get the hell out of there.
They performed the test in front of me and it came out negative (surprise surprise!). The whole ordeal took around 3 hours, and I pushed them to give me a lift to where I was going which they did.