Having interacted with some of the main proponents of the tripartite division of the law throughout history, and having interacted with some of their thoughts, we shall now entertain generic arguments for flaws in the tripartite assumption. As seen already, the tripartite approach is often accused of being arbitrary in its identification of the various categories of laws. This is because, by their own admission, the different precepts/law categories are not neatly divided, but intertwined. For example, reformed theologian Willem A. VanGemeren states,
The book of the Covenant (Ex. 20:22-23:33) – with its regulations for worship (20:22-26; 23:14-19) and its civil laws (21:1-23:13) – extends the Decalogue in three directions. First, there is the complex development of case law. … Second, the criminal laws specify the penalty for breaking the commandments. … Third, the book of the covenant reveals the complexity of Israelite law. The moral laws (i.e., those reflected in the Decalogue) are intertwined with the civil laws, penal code, and ceremonial laws.
To demonstrate this, he then proceeds to use Ex 22:19-29 as an example. In this passage, he shows that the topics covered vary from moral precepts, to penal precepts, to casuistic/civil precepts, back to moral precepts, and finally to ceremonial precepts, all intertwined in one passage. Reformed Professor John M. Frame is even more candid in his admission that the division between the supposed three parts of the law is not cut and dry. He tells us,
The law does not, of course, come to us with the labels "moral," "ceremonial" and "civil" attached to its provisions. What we call "moral" laws are mixed together in the texts (almost randomly, it seems) with "civil" and "ceremonial" laws, and we must sort them out by determining their meaning and current applicability. Those that apply most literally today we call "moral," those which apply least literally we call "ceremonial." "Civil" is a different kind of category, based not on applicability but upon function, and these would be divided between "ceremonial" and "moral" depending on their applicability. Remember too, that literal and non-literal applicability is a matter of degree, so we may expect some "gray areas," some laws that do not fit neatly into either "ceremonial" or "moral" categories.
His sorting process is quite different from the traditional assumption that only the Decalogue is the depository of moral laws, and after reading his decision making process, one is left to wonder if "applicability" is really a Biblical identification of morality. As can be seen, the lack of clear distinction between the three parts of the law does point to a lack of credibility for the tripartite division of the law.
Barrick picks up on this and stipulates that the,
Division into three categories of law is unmasked as a fallacy by the testimony of the Book of Deuteronomy alone. Moses’s second exposition (4:44—26:19) presented the Decalogue and then illustrated each of the Ten Commandments by means of various legal stipulations. Such an arrangement demonstrates that the so-called civil and ceremonial stipulations are inextricably interwoven with what are considered to be the moral laws. Violation of any of the stipulations is a breach of the Decalogue.
Another Old Testament text that does not square with the tripartite division of the law is Jer 31:31-2. Here God states that "Behold, the days are coming, says the LORD, when I will make a new covenant with the house of Israel and with the house of Judah-- not according to the covenant that I made with their fathers in the day that I took them by the hand to lead them out of the land of Egypt, My covenant which they broke, though I was a husband to them, says the LORD" (Jer 31:31-2 NKJV). If God has made a New Covenant which is not like the covenant at Sinai, is it acceptable for us to say that only parts of the Old Covenant have changed? There is nothing in this passage that allows the reader to accept that this is a renewal of the Old Covenant. After all, the term used here has a primary definition of "new," not "renew," and the text speaks of a New Covenant, not like the Old Covenant. It is hard to imagine that this would imply any kind of continuity with the Old Covenant. There is also nothing which substantiates the Calvinistic position that this is a reformatting of the Old Covenant, or even that it is a hyperbolic statement, for again, the promise is of a New Covenant, not just a new medium. Adeyemi also points out that "since the Old Covenant will be abolished, so will its Torah which cannot be divorced from it. ... This view accords with several statements in Isaiah about a Torah other than the Mosaic Law being given by Yahweh when Israel is in her land and Messiah is reigning."
Both Moo and Strickland also offer the Sabbath commandment as an exemplary test case of the abrogation of the Decalogue, and therefore as proof that if the Decalogue is the depository of God's immutable moral law, then even the moral law has changed. The argument goes like this: reformed theologians claim that the Decalogue is the eternal moral law. If that is the case, then all of the Ten Commandments should still be valid for New Testament believers. But the fifth commandment states that rest should be pursued on the seventh day, and since it is in the Decalogue, the lack of observance of the Sabbath in this way is a moral matter. Believers, including ones in the reformed tradition, have been meeting on the first day of the week since New Testament times, because it is sanctioned in the New Testament. Does that then mean that the eternal moral precepts are subject to revision and that God's nature has changed? Aquinas would not agree that God's nature has changed, neither would Calvin, and most probably, neither would modern reformed theologians.
Finally, looking at the use of the law in the New Testament, Moo argues that "Jesus and the New Testament authors treated the Mosaic law as a whole," and that "Jewish theology refused to allow a 'picking and choosing' among the commandments of the law." He also argues, by looking at Matt 23:23, that even though Jesus possibly followed a Jewish tradition of categorizing the law, he insisted that "even the 'light' commandments still must be done." He further points to Gal 5:3 and James 2:8-1, and their message of keeping or breaking the whole law, to suggest that the same perspective was adopted by the New Testament community.  Barrick picks up this same theme when he states that "to be disobedient to any one of the stipulations of the Mosaic Covenant is to be guilty of disobedience to all of the stipulations of the covenant (Jas 2:10)." Ultimately, Moo also analyzes Paul's use of the terms for the law and the reformed tradition's varied, and apparently arbitrary, interpretation of which laws Paul is referring to (moral or ceremonial law) and does not find any substantiation for their interpretations.
If the historical arguments for the tripartite law are flawed and if Scripture does not seem to support this idea, why is it so popular?
 Ibid., 30-1.
 Frame, 203-4.
 Barrick, 229.
 Femi Adeyemi, "What is the New Covenant 'Law' in Jeremiah 31:33?" Biblioteca Sacra 163 (July-September 2006): 315-9.
 Ibid., 320-1.
 Bahnsen et al., 81-2, 88.
 Aquinas Summa FS.Q100. A8.
 Calvin Institutes 4.20.15.
 Bahnsen et al., 85.
 Barrick, 231.
 Bahnsen et al., 85-6.