I disagree. Let's look at the verse more carefully and read what is there, not inserting your own theology into it:
For if we sin wilfully after we have received the knowledge of the truth, there remains no more sacrifice for sins...
Nothing about returning back to legalistic rituals - but to sin. Rituals are not sinful! God HIMSELF commanded them. The fact of the matter is that a person who willfully commits adultery, etc., is cutting themselves off from Christ's redemptive suffering. They are not in a "saved" status with the Lord.
Regards
Actually a number of Calvinist's commentaries that I have would disagree with my interpretation as well. They claim this refers to apostates in the end times as foretold by Christ. In any event all of them agree that while these people may give the appearance of being in the Church they are not of the Church for if they had been of the church they would have continued with the church. The end result is the same; people fall away.
Let me ask you under your interpretation,