It's even more legally funny than this. They are also allowed to enact entrapment to some degree and it passed court muster in the US. That because it's extremely hard to use it as a defence.

Note that these actions are illegal in most continental jurisdictions as stings must be devised ahead of time against specific groups of people. There's also Article 6 of ECHR.

In other words, FBI cannot run a sting off an EU site like this, at least definitely not a German one.