LawTeX not generating Table of Authorities

You need two compilation runs.

You have to do two compilation runs for output from the first run (e.g., page numbering) to flow through into the ToA in printable form on the second run. (see page 2 of the manual).

The reason is that information like page numbering is known fully only at the end of the first run; such information having been "parked" in the .aux file during the first run; the .aux file is read in at the beginning of the second run and its information inserted at the right spot.

I installed lawtex and tried your code.

After I defined a dummy Raich entry, and put in dummy values for compulsory fields, I get no error compiling under pdflatex (Lawtex uses pdfshellescape), and the usual two-pass run generates the table of contents and the index that is the table of authorities, as expected.

I have write18 enabled, so Lawtex automatically runs makeindex on each of the ToA parts (cases, statutes, other), so I don't have to do it manually between pdflatex runs.

MWE

providecommand{documentclassflag}{}
documentclass[12pt,documentclassflag]{lawbrief} 

usepackage[margin=1in]{geometry}
usepackage{newcent,microtype}
usepackage{setspace,xcolor}
usepackage[hyperindex=false,linkbordercolor=white,pdfborder={0 0 0}]{hyperref}

%%Citations

%The command makeandletter turns the ampersand into a printable character, rather than a special alignment tab
makeandletter

%We use newcase because the emph will throw off parsing in citecase

citecase{Scarborough v. United States, 431 U.S. 563 (1977)}
citecase{United States v. Morrison, 529 U.S. 598 (2000)}
citecase{United States v. Lopez, 514 U.S. 549 (1995)}
citecase{United States v. Stewart, 348 F.3d 1132 (9th Cir. 2003)}
citecase{Payne v. Tennessee, 501 U.S. 808 (1991)}
citecase{Smith v. Allwright, 321 U.S. 665 (1944)}
citecase{Wickard v. Filburn, 317 U.S. 111 (1942)}
citecase{Janus v. AFSCME, 585 U.S. (2018)}
citecase{Raich v. XXX, 999 XXX (9999)}%

index{Statute}{aa@textsc{U.S. Const.} art. I, S 8, cl. 3.|idxpassim}

newstatute{18 U.S.C.} {}
newarticle{Epstein}{Richard A. Epstein}{The Proper Scope of the Commerce Power}{73 VA. L. REV. (1987)}{1387}{}


%Set the information for the title page (later produced by makefrontmatter)
docket{No. 99-999} 
petitioner{p p p}
respondents{r r r}
circuit{em{n}th}
brieffor{Petitioner}
author{Anonymous # 999{em Counsel for Petitioner}}
address{123 Main Street  city state code (203) 555-1234}

questionpresented{{ q q q? doublespacingpar }}

begin{document}
%This commands creates the title page, table of contents, and table of authorities
makefrontmatter

%Sets the formatting for the entire document after the front matter
parindent=2.5em 
setlength{parskip}{1.25ex plus 2ex minus .5ex} 
setstretch{1.45}  

section{Argument}
subsection{Analysis Under Commerce Clause}
newpage
subsubsection{emph{Stare decisis} does not favor emph{Raich}}
newpage
subsubsection{emph{Scarborough} is not consistent with the Court's test under emph{Lopez}}
newpage
subsubsection{Machine guns have an ``attenuated effect'' on interstate commerce under emph{Morrison}}

``emph{Stare decisis} is not an inexorable command'' cite{Payne} and ``ldots when governing decisions are unworkable or are badly reasoned, ``this Court has never felt constrained to follow precedent.'' pincite{Smith}{649}. Considered by scholars under many lenses of Constitional interpretation, cite{Wickard} is generally viewed as a misstep in the grand scheme of this Court's historied jurisprudence on the Commerce Clause, especially in light of this Court's later rulings. See (``Could anyone say with a straight face that the consumption of homegrown wheat is `commerce among the several states?' '') pincite{Epstein}{1451}. When analyzing whether to adopt or overrule prescedent, this Court turns to four primary factors as established in cite{Janus}. Those being: the quality of the decision, the workability of the decision, developments since the decision, and reliance on the decision.  par

In addressing the first prong, the emph{Raich} majority heavily relies on emph{Wickard} even though this line of reasoning lies in direct conflict with both cite{Lopez} and cite{Morrison}. It appears Justice O'Connor shared this view, who dissenting in emph{Raich} wrote, ``[T]he Court appears to reason that the placement of local activity in a comprehensive scheme confirms that it is essential to that scheme. If the Court is right, then emph{Lopez} stands for nothing more than a drafting guide ldots'' cite[s]{Raich}(O'Connor, J., dissenting)
subsubsection{{The 9th Circuit's original analysis of emph{Stewart} was correct}}
end{document}