The sons of a man killed by a GP who administered a fatal overdose were arrested when they interrupted the doctor speaking at a conference.
Dr Daniel Ubani, 67, from Germany, injected David Gray, of Manea, Cambs, with 10 times the recommended dose of painkiller in 2008.
On Friday the GMC ruled Dr Ubani should be banned from practising in the UK.
Stuart and Rory Gray were held when they protested at a medical conference in Lindau, in Germany, on Saturday.
The pair said they wanted to know why Dr Ubani was still practising in Germany when he had been banned in Britain.
Rory Gray was charged with trespass and his brother Stuart, from Kidderminster in Worcestershire, was charged with trespass and verbal insults.
Both have now been released.