That link is just a copy of this original article: http://info.kopp-verlag.de/hintergruende/deutschland/udo-ulf....
Now if you look into this Kopp Verlag, you will find that the Verfassungsschutz is keeping an eye on them because they might be spreading right-wing ideology which seeks to overthrow the constitutional structure of Germany.
Interesting source for claims of unconstitutional behavior by Merkel ^^.
Now I'm not saying that any of this necessarily makes what they say untrue, but I guess your choice of sources makes one thing clear: Nobody here will be able to convince you.
Well, you found an actual federal judge that wrote an actual paper, even if you linked to some third rate news source instead.
Here's the paper: http://bayern.de/Gutachten_Prof_Di_Fabio
Here's a rebuttal: http://verfassungsblog.de/dem-freistaat-zum-gefallen-ueber-u...
He sort of, fairly timidly, questions it, with the flimsiest of legal analogies: the legislature has to agree to military missions, e.g. participation in UN missions, and thus (?!) something something Merkel. It's a complete non-sequitur.