Law? What is it good for?

The Westminster Confession of Faith 19.6 contains a helpful summary of why the law is of use, even to believers under the gospel, and allows us to see obedience as being natural under the gospel, rather than how it is used in American evangelicalism as a sign of "legalism" [improperly understood]. Here, I attempt to give an outline to help demonstrate this:

6. 
   a. Although true believers be not under the law, as a covenant of works, to be thereby justified, or condemned; [Romans 8:1]
   b. yet is it of great use to them, as well as to others; in that,
   
   1. as a rule of life informing them of the will of God, and their duty, it directs and binds them to walk accordingly;
      
   2. discovering also the sinful pollutions of their nature, hearts, and lives;
      
   3. so as, examining themselves thereby, they may come to further conviction of, humiliation for, and hatred against sin,
      
   4. together with a clearer sight of the need they have of Christ,
      
   5. and the perfection of his obedience.
      
   6. It is likewise of use to the regenerate, to restrain their corruptions, in that it forbids sin: and the threatenings of it serve to show what even their sins deserve;
      
   7. and what afflictions, in this life, they may expect for them, although freed from the curse thereof threatened in the law.
      
   8. The promises of it, in like manner, show them God's approbation of obedience, and what blessings they may expect upon the performance thereof: although not as due to them by the law as a covenant of works.
      [POINT:] So as, a man's doing good, and refraining from evil, because the law encourageth to the one, and deterreth from the other, is no evidence of his being under the law; and, not under grace.
      

Justification in Westminster Confession 11.1

I have yet to find a more succinct or accurate exposition of justification, especially in WCF 11.1:

"Those whom God effectually calleth, He also freely justifieth: not by infusing righteousness into them, but by pardoning their sins, and by accounting and accepting their persons as righteous; not for any thing wrought in them, or done by them, but for Christ’s sake alone; nor by imputing faith itself, the act of believing, or any other evangelical obedience to them, as their righteousness; but by imputing the obedience and satisfaction of Christ unto them, they receiving and resting on Him and His righteousness by faith; which faith they have not of themselves, it is the gift of God." -Westminster Confession of Faith 11.1

Westminster Confession Surprises

Many people from as diverse backgrounds as John Piper (Baptist) and J.I. Packer (Anglican) have praised the Westminster Standards as, in the case of Packer, “the greatest summation of the faith in English” to, in the case of Piper, “perhaps 98% agreement in my faith.” The Westminster Standards contains much that every Christian ought to hold dear: The Trinity, salvation by grace alone through faith alone, etc. It also holds some particularly Calvinistic truths: The Eternal Decree of God determining election, the total depravity of man, the perseverence of the saints, which still endear it to Calvinistic Baptists like Piper and Calvinistic Anglicans like J.I. Packer.

Yet, I also find it kinda funny, because I sometimes hear believers praise the Westminster Standards (The Confession and Shorter and Larger Catechism) which contain things that might fit into Piper's 2%, or be why Packer is not Presbyterian but Anglican, but I wonder if they know it. In studying the Westminster Standards, I've found several things I had not considered before. All but a couple, I have accepted and still consider myself comparing the last couple to Scripture to see if they are faithful in their interpretation. Some of the teachings that might hit us as peculiar:

Those in authority in the church are to be considered as “father” and “mother.” (LC 124)

Sacraments become effectual means of salvation by the Holy Spirit. (LC 161)

Only approved or ordained men ought to preach the Word (LC 158)

Outside of the visible church "there is no ordinary possibility of salvation" (WCF 25.2)

Those taking the Supper in faith truly feed on Christ. (LC 170)

Those who doubt should especially take the Supper. (LC 172)

Baptism rightly administered and received confers the grace which it promises. (WCF 28.6)

The Supper rightly administered and received conveys the grace which it signifies. (WCF 29.7-8)

The pope is the antichrist. (WCF 25.6 – original language, struck by the OPC and PCA)

Making any image of any Person of the Trinity is forbidden by the Second Commandment (LC109)

The Third Commandment forbids not taking a required oath in God's name, if by a lawful authority. (LC 113, WCF 22.2)

The Fourth Commandment forbids recreation on the Sabbath (LC 117)

Christians ought not marry unbelievers or papists (WCF 24.3)

Only adultery or willful desertion are grounds for divorce (WCF 24.6)