Yes, you can undo any Dynamic Parameter Action you have applied.
The Dynamic Parameter Actions currently active on a site can be seen on the 'Dynamic URLs' tab where you applied them and also along with the Delete URLs on the 'Actions' tab. You will see all Dynamic Parameter Actions that are applied for the site across all authenticated users of the site. You can 'Undo' them from either location, independent of which authenticated user applied the action.
Within a few days of your Undo, the URLs will stop being rewritten in the crawler and as they are recrawled, the original (non rewritten) versions of the URLs will start showing up. However, the ranking effects will continue to undo for a few months as all pages referring to your site are recrawled and links from them are reprocessed without rewriting.
Also, we keep some additional data around for the first few months after you apply a Dynamic Parameter action. This means that an 'Undo' performed in this period can recover more quickly. This allows a faster recovery from errors and unintended effects. However, after a few months, the additional data is lost which means that the 'Undo' recovery takes a little longer.
Note: If the person who requested the Dynamic Parameter Action, changes status, and becomes un-authenticated: