Medigap plans, or Medicare supplemental insurance plans, are regulated on both the federal and state levels. Because each state has different regulatory agencies and requirements, Medigap plans will be different from state to state. Where Medigap plans may be required to provide one service in California, they may not be required to do the same thing in Michigan. For complete details in what is available through your state you should contact the state department of insurance or your local Medicare office.
Qualifications for Medigap insurance is basically regulated by the federal government. These qualifications simply state that if you are qualified for Medicare, you can purchase a Medigap policy within a certain time frame of becoming eligible for the program. This 6 month eligibility period is known as open enrollment. During your open enrollment period you cannot be denied a policy, nor can you have any pre-existing conditions held against your policy. Also, during this period you must be charged a comparable rate as anyone else regardless of age, residence or health. Some states have open enrollment periods after this initial time frame, but this is a guarantee only given by the state and does not happen everywhere.
When you move across state lines you fall under the new states jurisdiction and are subject to their laws. Each state has a different regulatory agency for insurance products. When you move you have a limited time frame to change your Medigap policy to a carrier that functions within the new state. Many people find that they do not need to change because their insurer is allowed to practice in their new state. However, if they are not, you have a limited time to change to a company that serves your new state.