My roommate has his significant other staying overnight every night without having her pay rent or utilities. I want to know if there is any legal action I can take to force her to pay rent and/or utilities. If there is any legal precedent that could have her removed I would be interested in that also.

Do you have any kind of agreement with the roommate? Preferably IN WRITING? Are you the homeowner or are you renting a place together? If renting together, your lease with your landlord might have specific language about additional persons moving in. Is she keeping clothing there? Groceries? Is she getting mail there? Does she have a key? If so, the law might recognize her as a tenent - even if she never signed a lease, paid rent, or had your permission to be there. If THAT is the case, you'll have to go to court and have her evicted. The big problem with roommates is that each of you is generally held to have authority over the property - so even if you say no, if he says yes, you're back to square one.

Another strategy might be to give 1/3 of the money for rent and bills to the roommate and let him decide to either pay her share or ask her for it to make up the difference. Of course if the rent and utilities are in your name and he doesn't pay them, you'll be stuck with not only the bills, but the damaged credit as well.

Ultimately, a court might find that he violated your agreed-upon living arrangement, but you'd have to take him to court to find that out - which usually doesn't bode well for him sticking around to pay at least his half. You might just remind him that you have the option to sue for the rental difference due to the contract violation, and see where it goes from there. Would you be able to afford to live there without him/them?

Have you tried to talk to him about her staying over?

We do not have a written agreement because he did not mention that she would be moving in to me until she had already done so. She does have a key and keeps clothing and groceries at our place. The utilities are in both mine and my roomates names.

And to answer the moderator, yes I have told him that I dont care for her or her staying over every night to which he replied "Deal!".

Sounds to me like she would be considered a tenent, in which case, if she won't go willingly, you'll have to go to court to have her evicted. Just be aware that if she goes, he might go with her and then you might end up paying rent alone. (Of course you could then sue HIM for his half of the rent, but even if you win you'll then have to go through the collection process which is NOT a walk in the park.) You'll have to figure out the pros and cons as far as is it worth putting up with her to have at least one person who's splitting bills vs. the cost and time to go to court and then the hassle of collections (during which time you'd be on your own to pay or quickly find a new roommate).