Klaus Balkenhol and Hans-Heinrich Isenbart (among others) have formed the Xenophon Society. It’s stated goals are:
a) the preservation and promotion of riding culture in accordance with traditional, classical principles;
b) the education about the dangers of violating the principles of the classical doctrine for the sport of riding;
c) the application of the “Ethical Principles of Horse Lovers” to the practice of riding, in accordance with § 15 of the present Bylaws;
d) the raising of awareness about the classical riding culture;
e) the promotion of training of riders and horses, and
f) the promotion of a good reputation of equestrianism in the public eye, as well as in general;
g) the promotion of the principles of protection of animals when keeping, handling and training horses;
h) the promotion of science, research, literature, and applications in all fields of horse-related activities, as well as
i) the observance of the Association’s purposes in the framework of its non-profit activities vis-à-vis other equestrian organizations.
Its website is http://www.truemner.net/xenophon/ The website is in English, German and Dutch.
You might want to check it out.