I was surprised by this, like other sibling commenters. I was under the impression that common assault is only enacted when the victim is threateningly contacted or injured, or has reasonable fear of that being about to happen. Maybe threatening language might play a part in that.
Having a quick Google, the articles I've come across seem to indicate that swearing at police has in the past been interpreted as illegal, but nothing has mentioned it being classed as assault.
There's section 5 of the public order act which is about saying / doing things "likely to cause harassment, alarm or distress" to the public, which has been interpreted as including police officers. I don't know anything about having to say things twice or it being classed as assault.
There was a 2011 ruling in England where the judge said that officers were so regularly on the receiving end of the "rather commonplace" expletive that it was unlikely to cause them "harassment, alarm or distress".
The Met continues to arrest people for swearing at police as they rejected the ruling. I know that Police Scotland continue to arrest people for swearing at police but I'm not sure how/if it has affected forces in England and Wales. At the time it was reported that the precedent could likely quash any future charges in similar circumstances.
There's 2011 advice provided to the Met which says that courts are unlikely to convict because officers are assumed to be robust: http://www.bbc.co.uk/news/magazine-15816761
It's probably a bad idea to direct insults at officers (because no-one likes being called a fucking facist wanker) and results will vary by location.
I'm not sure, but I think that after the first time the officer should say "don't use that language at me" and therefore probably tells the citizen that they are causing harassment and distress. Then if they continue to do it, after the warning, it becomes an offence. So perhaps it should be "continues to use offensive language after a warning about the language has been given".
It's illegal in Germany as well ("Beamtenbeleidigung" literally insult of a civil servant). The fines are pretty mild but it's a funny law (imo). The line isn't exactly clear. Some things qualify as insults, others don't.
Iirc "Clown" qualifies but "Bulle" (somewhat similar to the US use of pig=cop) doesn't because it is considered common use now.
The rulings usually seem arbitrary.
[The same laws apply for insulting non officers btw.]
Edit: Upper limit is technically one year in prison or a corresponding monetary fine (value depends on your income as is standard in Germany)
There is no such thing as a "Beamtenbeleidigung" in Germany, though it is a quite common myth. People in office enjoy no special rights in that regard. There is a difference, though, in the law process. Insults as a criminal offense need a personal demand for a penalty to warrant persecution by the state. For people in office, this can be replaced by a substitution demand by the state, supposedly to warrant respect for office in general.
Then, there isn't a catalogue for insults and their penalty. That's because criminal law in Germany is driven by the idea that the thing to be penalised is the individual guilt, rather than an objective action. This has a lot of consequences, one of them being that your action is weighted by what you wanted when doing the potentially criminal action, i.e. the intent.
