Getting ticket for passing cop

Speed limit was 100km/h, cop was doing 90 in the middle lane, I was behind him and decided to pass, I went to the left lane (fast lane) doing about 100-103 and passed him then I went back to the middle lane all using blinkers signaling my intentions. He immediately stopped me signaling with the flashing lights. He said it's illegal for me to pass him and go in front of him. He didn't mention speed just that then wrote me a ticket.

Is this right? I mean, I didn't brake check him or obstruct him in any way, while passing him I was constantly monitoring my speed so thats how I knew my speed was 100-103 but seems like I got a ticket for just passing and going in front of him.