From the letter of Mr. Hoyle to the followers of the Dimonds: "Frederick's policy that entrants to MHFM must transfer their assets to the “monastery” is in flagrant
violation of the 1917 Code of Canon Law, which has provisions to safeguard the property of entrants into a religious community" https://tradcath.proboards.com/thread/2165/letter-followers-dimond-bros-hoyle
Canon 568
In the course of the novitiate, if a novice renounces his benefices or goods in any manner or encuмbers [them], the renunciation or obligation is not only illicit, but by the law it is invalid.
Canon 570
Whatever the aspirant brought and has not consumed by use shall be restored to him if he leaves the religious [institute] without having given profession.
I guess when Mr. Hoyle left he has already made his profession: "there was no novitiate at all at MHFM, in the sense of a period of instruction and
spiritual formation in preparation for life as a consecrated religious. There was no program of studies;
there was no change in my daily routine when I became a novice or when I became a professed monk."
So technically Canon 570 couldn't apply since he made his profession, but since his handing over all his money happened while still a postulate, it was invalid anyway, and he had the right to take back his money that wasn't already spent, since they had no right to ask him to hand over all his money when he was still a postulate.
Related source treating the issue: http://www.23rdstreet.com/mhfm/eric_hoyle.aspx