"To take legal action" means to start a legal process or pursue a lawsuit against someone in order to resolve a dispute or seek justice through the courts. Full definition
If you sustained a neck injury in a car accident and are interested in taking legal action against the liable party, you may need the representation and guidance of a knowledgeable attorney. (craigswapp.com)
We will take legal action if necessary to hold them responsible and accountable for any unlawful behavior. (newsroom.fb.com)
This doesn't mean that the lender can not take legal action in order to recover his money. (badcreditloanservices.com)