Who legally has the right to serve summons?

I'm a bit confused because everywhere it's written that summons are often served by TCCs nowadays, but according to deputies and the military ombudsman, this is not their responsibility at all, and by law, local administrations or law enforcement should be doing it. So who, according to the law, should actually distribute summons for mobilization, and is it even legal if I am given one by TCC employees on the street?