Owen makes use of his (1689 Federalism’s) distinction between the promised/established New Covenant. The establishment of the New Covenant refers to it’s being “reduced into a fixed state of a law or ordinance.”
That which before had no visible, outward worship, proper and peculiar unto it, is now made the only rule and instrument of worship unto the whole church, nothing being to be admitted therein but what belongs unto it, and is appointed by it. This the apostle intends by nenomoqe>thtai, the “legal establishment” of the new covenant, with all the ordinances of its worship… The first solemn promulgation of this new covenant, so made, ratified, and established, was on the day of Pentecost, seven weeks after the resurrection of Christ. (Comments on Hebrews 8:6)
From this framework he addresses Hebrews 6:3-6. He correctly notes that the passage has primary reference to Jews who had converted from Judaism by professing faith in Christ. Thus the passage has to do with the historical differences between the Old Covenant and the New Covenant.
That all these privileges do consist in certain especial operations of the Holy Ghost, which were peculiar unto the dispensation of the gospel, such as they neither were nor could be made partakers of in their Judaism… The whole description, therefore, refers unto some especial gospel privileges, which professors in those days were promiscuously made partakers of…
The Holy Ghost is here mentioned as the great gift of the gospel times, as coming down from heaven, not absolutely, not as unto his person, but with respect unto an especial work, namely, the change of the whole state of religious worship in the church of God; whereas we shall see in the next words he is spoken of only with respect unto external, actual operations… But when he came, as the great gift of God promised under the new testament, he removes all the carnal worship and ordinances of Moses, and that by the full revelation of the accomplishment of all that was signified by them, and appoints the new, holy, spiritual worship of the gospel, that was to succeed in their room. The Spirit of God, therefore, as bestowed for the introduction of the new gospel-state, in truth and worship, is “the heavenly gift” here intended… And there is an antithesis included herein between the law and the gospel; the former being given on earth, the latter being immediately from heaven. God in the giving of the law made use of the ministry of angels, and that on the earth; but he gave the gospel church-state by that Spirit which, although he worketh in men on the earth, and is said in every act or work to be sent from heaven, yet is still in heaven, and always speaketh from thence, as our Savior said of himself, with respect unto his divine nature, John 3:13…
That, therefore, which is ascribed unto these persons, is, that they had an experience of the power of the Holy Ghost, that gift of God, in the dispensation of the gospel, the revelation of the truth, and institution of the spiritual worship of it; of this state, and of the excellency of it, they had made some trial, and had some experience; — a privilege which all men were not made partakers of… The meaning, then, of this character given concerning these apostates is, that they had some experience of the power and efficacy of the Holy Spirit from heaven, in gospel administrations and worship.
The passage does not teach that one may be a member of the New Covenant and fall away… unless of course you come to the text with the preconceived belief that professing faith and participating in New Covenant worship makes you a member of the New Covenant.