Answer by Gonzalo Medina for Different section numbering styles for toc and body

The titlesec package can be used here. The modifications to the .sty file:

\ProvidesPackage{aglc}\NeedsTeXFormat{LaTeX2e}\RequirePackage{parskip}\RequirePackage{chngcntr}\RequirePackage{titlesec}\setcounter{secnumdepth}{5}\setcounter{tocdepth}{5}\counterwithin*{subsection}{section}\counterwithin*{paragraph}{subsection}\counterwithin*{subparagraph}{paragraph}% AGLC Heading 1% I Section\renewcommand*\thesection{\Roman{section}}                                      \renewcommand\section{\@startsection {section}{1}{\z@ }%    {-3.5ex \@plus -1ex \@minus -.2ex}%    {2.3ex \@plus  .2ex}{\normalfont \centering \large \sc }}% AGLC Heading 2% A SubSection\renewcommand*\thesubsection{\Alph{subsection}}  \renewcommand\subsection{\@startsection {subsection}{2}{\z@ }%    {-3.25ex\@plus -1ex \@minus -.2ex}%    {1.5ex \@plus .2ex}{\normalfont \centering \large \emph }}% AGLC Heading 3% 1 SubSubSection\renewcommand*\thesubsubsection{\arabic{subsubsection}}\renewcommand\subsubsection{\@startsection {subsubsection}{3}{\z@ }%    {-3.25ex \@plus -1ex \@minus -.2ex}%    {1.5ex \@plus .2ex}{\normalfont \emph }}% AGLC Heading 4% (a) Paragraph\renewcommand*\theparagraph{(\alph{paragraph})}\titleformat{\paragraph}  {\normalfont\normalsize\em}  {\renewcommand*\theparagraph{%      \arabic{subsubsection}(\alph{paragraph})}\theparagraph}  {1em}{}\titlespacing*{\paragraph}  {0pt}{3.25ex plus 1ex minus .2ex}{1.5ex \@plus .2ex}% AGLC Heading 5% (i) SubParagraph\renewcommand*\thesubparagraph{(\roman{subparagraph})}\titleformat{\subparagraph}  {\normalfont\normalsize\em}  {\renewcommand*\thesubparagraph{%      \arabic{subsubsection}\theparagraph(\roman{subparagraph})}\thesubparagraph}    {1em}{}\titlespacing*{\subparagraph}  {0pt}{3.25ex plus 1ex minus .2ex}{1.5ex \@plus .2ex}\newcommand{\case}[1]{\emph{#1}}\newcommand{\caseref}[1]{[\emph{#1}]}\newcommand{\statute}[2][Qld]{\emph{#2} (#1)}\newcommand{\latin}[1]{\emph{#1}}\endinput

Since titlesec was used to change the formatting for \paragraph and \subparagraph, it could also be used for the other sectional units.

Here's a simple test document using the aglc.sty file to show the desired changes in action:

\documentclass{article}\usepackage{aglc}\usepackage{lipsum}% just to generate text for the example\begin{document}\tableofcontents\section{Test section}\subsection{Test subsection}\subsubsection{Test subsubsection}\paragraph{Test paragraph}\lipsum[2]\subparagraph{Test subparagraph}\lipsum[2]\end{document}

And the resulting document:

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