Legal Question in Civil Litigation in Maryland

Your question seems to involve a complex mix of real estate, civil, domestic and criminal law. It is beyond the scope of an online post to fully answer and you would likely benefit from getting competent legal representation. An online open answer can offer general legal information but not detailed legal advice.

Generally speaking, co-owners each have the full right to occupy property they jointly own. Usually one owner cannot force out another owner without a court proceeding. However there are a few different legal proceedings or orders that can impact these rights. A protective order can restrict someone from going to their property. Similarly, if someone has custody of minor children the courts may issue a "use and possession" order giving one spouse or the other rights to exclusively occupy the marital home with the children, even if the spouse with custody doesn't own the house.

It isn't clear how the property is titled but the post seems to imply that both spouses are on title and only one on the mortgage.

It gets very complicated when one spouse invites another person to move into the marital home without permission of the other spouse. The law frankly was not structured to deal very well with one spouse inviting a third party into the marital home - there are legal doctrines like ouster, partition, accounting, sale in lieu of accounting and such that can apply to joint owners but they don't apply very well to marital property owned during the marriage. Generally, if someone owns property they have a right to live there (unless there is a court order saying otherwise). Generally, once someone moves in, a non-owner occupant needs an eviction proceeding to be removed unless they agree to move out.

Where a husband and wife own property together as tenants by the entirety the law looks at this as the marital unit owning the property. Yours is not the first situation where one spouse invites a third party into the house and you may want to consult with an experienced family law attorney. Often issues related to real estate get resolved in a separation agreement and/or divorce proceedings. Either an absolute or if there is no desire for a full divorce, a limited divorce (literally from bed and board) might address some of these issues.

Again, this general information does not substitute for getting legal advice. Some family law attorneys in this state volunteer their time at self-help family law clinics, usually held in the Circuit Court, and may be able to help guide as to the different court forms related to custody and divorce. Eviction related information and forms are available at the District Courts and a few District Courts may have volunteer attorneys available to help guide with forms related to the eviction process.