If you read the same verses in the amplified version, i think it will clarify the full intent and meaning...
Also you cannot take this statement out of its context, here the context that Shaul was talking about was about the priesthood. This is all that is mentioned after the statement that Shaul made regarding changing the law... Shaul could only mean one thing, changing the law regarding the priesthood.
Heb 7:11 onwards...
11Now if perfection (a perfect fellowship between God and the worshiper) had been attainable by the Levitical priesthood--for under it the people were given the Law--why was it further necessary that there should arise another and different kind of Priest, one after the order of Melchizedek, rather than one appointed after the order and rank of Aaron?
12For when there is a change in the priesthood, there is of necessity an alteration of the law [concerning the priesthood] as well.
13For the One of Whom these things are said belonged [not to the priestly line but] to another tribe, no member of which has officiated at the altar.
14For it is obvious that our Lord sprang from the tribe of Judah, and Moses mentioned nothing about priests in connection with that tribe.
15And this becomes more plainly evident when another Priest arises Who bears the likeness of Melchizedek,(A)
16Who has been constituted a Priest, not on the basis of a bodily legal requirement [an externally imposed command concerning His physical ancestry], but on the basis of the power of an endless and indestructible Life.
17For it is witnessed of Him, You are a Priest forever after the order (with the rank) of Melchizedek.(B)
18So a previous physical regulation and command is cancelled because of its weakness and ineffectiveness and uselessness--
19For the Law never made anything perfect--but instead a better hope is introduced through which we [now] come close to God.
20And it was not without the taking of an oath [that Christ was made Priest],
21For those who formerly became priests received their office without its being confirmed by the taking of an oath by God, but this One was designated and addressed and saluted with an oath, The Lord has sworn and will not regret it or change His mind, You are a Priest forever according to the order of Melchizedek.(C)
22In keeping with [the oath's greater strength and force], Jesus has become the Guarantee of a better (stronger) agreement [a more excellent and more advantageous covenant].
23[Again, the former successive line of priests] was made up of many, because they were each prevented by death from continuing [perpetually in office];
24But He holds His priesthood unchangeably, because He lives on forever.
25Therefore He is able also to save to the uttermost (completely, perfectly, finally, and for all time and eternity) those who come to God through Him, since He is always living to make petition to God and intercede with Him and intervene for them.
26[Here is] the High Priest [perfectly adapted] to our needs, as was fitting--holy, blameless, unstained by sin, separated from sinners, and exalted higher than the heavens.
27He has no day by day necessity, as [do each of these other] high priests, to offer sacrifice first of all for his own [personal] sins and then for those of the people, because He [met all the requirements] once for all when He brought Himself [as a sacrifice] which He offered up.
28For the Law sets up men in their weakness [frail, sinful, dying human beings] as high priests, but the word of [God's] oath, which [was spoken later] after the institution of the Law, [chooses and appoints as priest One Whose appointment is complete and permanent], a Son Who has been made perfect forever.
