A German satirist, Jan Boehmermann, presented a vicious rap/poem/song on a show he hosted on the ZDF network, attacking Turkish president Erdogan.  A synopsis of the scandal can be found here, Boehmermann's wiki entry.

I was in Germany when the crap hit the fan over this satire.  It got ugly.  Boehmermann lost his show and had to go into hiding.  There were competing pro-Erdogan and anti-Erdogan demonstrations which had to be separated by cordons of riot police and horse-mounted cops.  (I had to navigate around one when it took up the streets outside my hotel.  Scary.  German police are quite nice and professional, until they are not.  Then, watch out.)  Erdogan briefly made threats to send more refugees into Germany and a whole bunch of other diplomatic tantrum stuff.

Merkel pretty much had to turn this over for prosecution because of the state of the law in Germany then.  It was quite embarrassing to the German government because, not only were they forced to go against their tradition (tradition - not law:  No First Amedment there) of  "meinungsfreiheit"  (freedom of opinion/speech) but also because it threw a real monkey wrench into diplomatic efforts trying to address the massive refugee flow (thru Turkey into Europe) and also the government's efforts to tamp down the resurgent right-wing anti-immigrant populism of PEGIDA, AfD and also the neo-Nazis.  That right-wing populism, in turn, had really been agitated by a New Years' Eve ('14-'15) incident in Cologne where bands of Middle Eastern refugee men had surrounded and groped (to put it politely) any woman they could find, only to allegedly proclaim to police things like "Mrs. Merkel invited us here so you can't arrest us." and such.  That whole incident, the police initially tried to cover up by not reporting it at all.  Which, of course, just made it worse when it came out.

So, Boehmermann threw a bundle of burning road flares into an overturned gasoline tanker, so to speak.  He was fired, has to be in hiding (I believe Erdogan put a price on his head though that was never actually reported), and was facing criminal prosecution.

Before Christmas the prosecutors decided there would be no prosecution.  This change in law could then come about.

Germany has repealed a law allowing prosecution of those who criticize foreign leaders. It takes effect 1/1/2018.