Nested Enumeration

\documentclass[numbers=endperiod]{scrartcl}

\addtokomafont{section}{\rmfamily\mdseries}

\renewcommand*{\theenumi}{\thesection.\arabic{enumi}}
\renewcommand*{\theenumii}{\theenumi.\arabic{enumii}}
\renewcommand*{\theenumiii}{\theenumii.\arabic{enumiii}}
\renewcommand*{\theenumiv}{\theenumiii.\arabic{enumiv}}

\renewcommand*{\labelenumi}{\theenumi.}
\renewcommand*{\labelenumii}{\theenumii.}
\renewcommand*{\labelenumiii}{\theenumiii.}
\renewcommand*{\labelenumiv}{\theenumiv.}

\makeatletter
\renewcommand*{\p@enumi}{}
\renewcommand*{\p@enumii}{}
\renewcommand*{\p@enumiii}{}
\renewcommand*{\p@enumiv}{}
\makeatother

\begin{document}
\section{Information About Us}

\begin{enumerate}
 \item This website is run by the Secret Lab of Experimental Stuff 
  (``We'', ``Our''). We operate from the University of Somewhere.
\end{enumerate}

\section{Our Products}

\begin{enumerate}
 \item All Products shown on our site are subject to availability.

 \item You may only purchase our products if you are at least  
  18 years old.
\end{enumerate}

\section{Refunds}

\begin{enumerate}
 \item You are entitled to a refund unless:
 \begin{enumerate}
   \item you have eaten the mind-controlling cookies;
   \item you have thrown the exploding chocolates;
   \item you have used the ray gun as:
   \begin{enumerate}
     \item a table chock;
     \item a weapon unless:
     \begin{enumerate}
       \item \label{permit}you have a ray gun permit;
       \item you are an extraterrestrial.
     \end{enumerate}
   \end{enumerate}
 \end{enumerate}
\end{enumerate}

Now for a cross-reference. See clause~\ref{permit}. 

\end{document}
Download sample-enum.tex or sample-enum.pdf.