In order to clear AppLocker policies from a machine you must use the Set-AppLockerPolicy cmdlet with the -XMLPolicy parameter using a .XML file which contains the following contents:
<AppLockerPolicy Version="1">
<RuleCollection Type="Exe" EnforcementMode="NotConfigured" />
<RuleCollection Type="Msi" EnforcementMode="NotConfigured" />
<RuleCollection Type="Script" EnforcementMode="NotConfigured" />
<RuleCollection Type="Dll" EnforcementMode="NotConfigured" />
</AppLockerPolicy>
To use the Set-AppLockerPolicy cmdlet, we must first import the Applocker modules. To do this:
PS C:\Users\Administrator> import-module AppLocker
We will create a file for example called clear.xml and place it in the same directory that we are executing our cmdlet. And fill it with the XML Contents above. Then you must execute using the following command:
C:\Users\Administrator> Set-AppLockerPolicy -XMLPolicy .\clear.xml
This will remove all AppLocker Policies on a machine and could be potentially scripted to use on multiple machines using remote execution tools with accounts with proper access.