There may be important facts not included in your request. For openers, is this a private or a public street? The laws are different for each. Was the car towed by a municipal agency or agent or by a private tow company enforcing private "no parking" laws? Even if the tow would be unlawful because of non-conformity with applicable statutes regarding notice and signage, your target may not be the city if the tow company was enforcing a private parking restriction.
If you want to pursue this matter rather than just pay the towing and impound fees to get your car back, you will need to consult with an attorney in your area to be sure of your legal grounds based on the relevant facts.
"The law" is a very complex profession, and all specific legal questions will depend on a variety of facts that you may not think to include in your questions on this forum. I am not your attorney, and in answering your question you must understand that I cannot and do not give you legal advice upon which you are entitled to rely. At best, I hope that my answer, and others you find here, will give you a basis for better understanding of the issues you face so that you can provide complete information to a lawyer that you retain to give you advice and representation on which you can confidently rely.