This is a valid question that comes up from time to time. The answer can be a bit fuzzy and the law on questions 1 and 2 is often not well spelled out. This answer refers only to U.S. legal history without much customization for Maryland in particular, so I may omit references to some relevant Maryland specific statutes or cases of which I am not aware.
Often there is no statutory guidance or there is only inconclusive or vague statutory guidance. There is often also little appellate case law precedent to provide guidance.
The issue comes up far more often than it is litigated, in part, because these issues tend to become moot before they can be resolved by a precedent creating appellate court, and because statutes addressing the issue tend to be recent and not yet litigated, or non-existent. These issues are often highly time sensitive and don't have an economic prize to spend money litigating over are often not litigate to the maximum extent. Court rulings when cases are presented to them often depend a lot on the procedural context of the way the issue comes up, how the issue is framed by the litigants, and upon the court's gut feelings and upon unwritten social norms.
For example, one recent case involving the ability of a priest to visit a man who was sick with COVID-19 in a Maryland hospital notwithstanding hospital visitation policies was resolved in the context of a complaint to the Maryland Office of Civil Rights and would not be generally applicable to an intrafamily dispute as opposed to an allegation of religion based discrimination.
The hospital's opinion is often given outsized weight, since it is a "neutral" party in a family dispute, has a vested interesting in having litigation resolved that is more economic than that of the family members, and is likely to have counsel that is most familiar with the issues presented. this is true even though often, a hospital has a religious affiliation or is for some other reason specific to the facts of a case is not truly a "neutral" party in a visitation dispute and takes a position for a non-medical reason.
As a young lawyer at a law firm that represented a hospital, I handled cases like these for a hospital when they came up for a couple of years, because nobody more experienced wanted to deal with these emotionally draining and time consuming conflicts with few monetary rewards for the hospital, and because the stakes from the hospital's perspective were low, so junior associate attorneys could be trusted with this cases.
Appellate courts also often frame these decisions as fact bound case by case questions decided under general considerations applicable to all forms of injunctive relief in civil cases, rather than questions presenting more general questions of law to which general policy rules apply.
Furthermore, the conceptual foundation in which we think about the authority of different family members over an incapacitated person at common law has shifted materially since the 19th century when these issues started to arise, and mostly hasn't been formally discussed by the courts as applied to these particular situations in the meantime.
So, even when there are old precedents governing these situations, there is doubt regarding whether they are still good law, because the old precedents are based upon assumptions about spousal and parental and family member rights that no longer hold in other areas of the law.
See also an analysis of issues of visitation and medical decision making for disabled persons, primarily under the federal Americans with Disabilities Act and related regulations, with footnotes particular to Maryland's state laws on the subject.
Can E block B, C and D from visiting A in the hospital?
What legal authorization form(s) can person A fill out and provide to B, C and D to prevent that from happening if this is a serious
The right of a private individual to visit someone in a hospital is usually not codified into law and is usually a matter of hospital policy within reason, acting in the best interests of its patients from a medical perspective.
Usually E could only block B, C and D from visiting A in the hospital (1) with the cooperation of the hospital based upon its own policies (since as a practical matter, the hospital is generally in control of the situation and has broad authority to restrict access to its patients for health reasons), or (2) with a restraining order or protective order obtained from a court, or (3) as a legal guardian appointed by a court of person A (who generally has the authority to decide who their ward can interact with).
In old common law cases (usually mid-19th century or earlier, but sometime in the early 20th century), the spouse of a married person (sometimes only the husband of a wife, but not visa versa), or the parents of an unmarried minor or unmarried person more generally, had the rights of a legal guardian with respect to an incapacitated person, and a family member had authority to make decisions for an incapacitated person as next of kin, in the absence of a parent or spouse.
But, for the most part, this is no longer legally enforceable law.
The Married Women's Property Acts of the late 19th century and early 20th century generally eliminated the authority of a spouse to act as legal guardian of an incapacitated spouse without a court order, sometimes subject to cases of "necessities", and control of personal family property like a marital residence, household goods, or vehicle titled in a spouse's name alone that the competent spouse used in the ordinary course prior to the incapacity.
The authority of a parent or next of kin person to take action for an incapacitated person without a court order was largely abrogated by state probate codes establishing court procedures for guardianship and conservatorship appointments for incapacitated people giving spouses, parents and next of kin priority, but not authority in the absence of a court order, except in the case of minor, unmarried, unemancipated minor children. And, even then, it is rare for statutes for expressly grant parents that authority over the children by statute and the authority is merely assumed as background common law to other statutes limiting that authority in cases of child abuse or child neglect, and some kinds of decisions still need court approval even in the case of parents of unemancipated, unmarried minor children.
Documents specifically authorizing visitation are rare (I've never seen one in real life outside a civil union of a same sex couple), although states with "civil union" laws enacted before same sex marriage was legalized, often expressly afford a civil union partner visitation rates with priority over other family in hospitals, despite the fact that the status quo law is often ill defined. Hospital policies that denied visitation to de facto civil union partners were an important driving force in causing civil union legislation to be adopted with the support of legislators who didn't have a strong feeling about gay rights as an overall matter and who were otherwise indifferent to the economic rights of civil union matters but adopted the rights of married couples because it was the mindless default way to adopt a body of pre-existing law with little serious thought or fact rich informed deliberation.
This is, in part, because visitation is not a matter over which a patient at a hospital has unilateral decision making power. Hospitals generally have their own policies regarding visits to patients. See, e.g.,, discussing the University of Maryland's hospital visitation policy.
Usually, a hospital will honor a patient's reasonable request to not allow someone to visit them (out of general respect for patient autonomy). But, a hospital will often decline to allow a patient to have visitors out of concern for the best interests of the health of the patient even when a patient would like to have a visitor (e.g. a hospital would often refuse to allow someone with a recent positive COVID-19 test to enter an Intensive Care Unit (ICU) even if the patient would like to visit that person).
Even here, however, the conceptual foundation behind traditional hospital practices related to visitation have shifted. The modern view is to more strongly respect the personal autonomy interests of a hospital patient than hospitals did in the past (the trend started to shift more strongly to a patient autonomy mindset in the late 1950s and gradually shifted toward greater patient autonomy in that time frame, particularly, following the deinstitutionalization of the mentally ill).
Hospitals are loathe to create a situation where their express statutory, contractual, and/or common law authority to regulate visitation could be overridden by a patient, and laws related to hospital visitation are rarely adopted by a legislature over the objection of the hospital lobby.
- What legal authorization form(s) can person A fill out and provide to B and C so that they get precedence in medical decision-making
authority over E?
Many hospitals would give E priority over B and C and D in making medical decisions for A, if A is incapacitated and there are no court orders or legal documents that provide otherwise, as a matter of policy. And, these policies are often traceable to the mindset associated with the old common law rules that no legal have binding legal effect.
But some states have a scheme in which the hospital makes unilateral decisions in the best interests of the patient as they see it, unless B, C, D and E (and possibly other people designated by mutual agreement) jointly agree on who should make those decisions. See, e.g., Colorado Revised Statutes § 15-18.5-103 (Proxy decision-makers for medical treatment authorized--definitions). On paper, Colorado is such a state, although in practice, a hospital would offer listen to a spouse over other family anyway.
I don't know if Maryland is such a state. I could not easily locate any statute in Maryland governing medical decision-making authority for an incompetent patient in the absence of a health care power of attorney or the equivalent or a guardianship proceeding, although my search was not exhaustive.
A document commonly known either as a medical power of attorney, or a health care power of attorney, or a health care proxy designation made by a competent person who does not have a legal guardian appointed for them at the time, can designate someone such as B and C to have priority over E in making medical decisions for them. This document would be controlling absent a court order to the contrary, and usually a court would give authority to the person named in that document (although a court is almost never required to do so without regard to the suitability of the person seeking court ordered decision making power).