Question: There is a particular recruiting company that continues to contact me. I have been unhappy with their performance in the past and have been clear that I am no longer interested in their services. I have had to inform them of this multiple times.

Whenever they contact me, I inform them that I do not want them to contact me further. They oblige for a few months, and then I get an e-mail or phone call from a different recruiter with the same company. Most recently, I expressed my frustration and insisted that I be completely removed from their database. Today, I received another e-mail from them after months of silence.

Is there any sort of legal grounds I can quote or anything else I can say or do to force them to *actually* remove me from their list of contacts and stop contacting me?

Answer: 
First step - Check the recruitment companies privacy and/or communication policy.

Second step - For most Western Countries, there will be a Privacy Commissionaire who you can report them too (just make sure you have documented proof that you have requested them to remove your personal details/information from their records)

Third step - Search out and contact the Association body for recruitment/staffing firms (NAPS, ACSESS, REC, etc... and Better Business Bureau).

Fourth step - Draw up a 'Cease and Desist Letter' - would strongly recommend using legal guidance (it might cost but if you feel this strong then it shows you are serious). Each state/prov/country has rules, terms, conditions, and you want to make sure you include terms such as 'breach or privacy', 'harassment' and 'feeling threatened' and 'mental duress'.

Additionally, if you are connected to anyone from that company on social media sites - communicate your intention and desire to be removed from their system, and go as far as disconnecting from them, un-following them, and blocking them.
Is your resume posted on a job board such as Monster? If so, I don't think the recruiter **is** keeping you in their database.

I get a lot of calls from recruiters, including those I've sent my resume to in the past. They often say that they found my resume on a job board, not in their own database. (I can confirm that, based on the e-mail addresses I use in different resumes.) 

I'm fairly certain that this company really does remove you from its list, but a few months later their agents simply **rediscover** you, along with many other candidates.

I suggest that your resume (at least, the one you put on the job boards) have only a Google Voice phone number. Not only don't you have to answer it, but the voicemails can be sent to you as e-mail, so you don't have to play them back.