There are many ways that one can change his “legal status”. So, long was these actions that change a person’s legal are taken voluntarily, libertarianism will accept them. In most societies, the first change of legal status occurs by a change of age. For example, in most states in the United States, a person cannot enter a contract and be bound by it until he or she reaches the age of 18. At this age, whatever it my be, a person’s legal status changes from juvenile to adult. Siimilarly, a person juvenile is treated differently than an adult for punishments from criminal activity.
If by “signing a contract” you mean voluntarily entering a contract (not all contracts have to be signed to be binding), then yes your legal status changes. By entering a contract you have agreed to give up title to some type of property in exchange for a different item of property. Your legal status as owner of the old property has changed since you are no longer the owner; it also changes as you become the owner of the new item of property. So long as, one voluntarily enters a contract, the change in legal status should be acceptable under libertarian theory.
A marriage contract is somewhat uniqe and may not be acceptable. When a person gets married into today’s society, both parties automatically enter a contract. The specific terms are imposed by law and the parties may or may not be aware of them. It is difficult to say the parties have entered voluntarily a contract when they do not even know the terms. Most people do not come to know the terms of the married contract until they get divorced. This does not seem consistent with libertarian theory. The parties have not selected voluntarily the terms.
Another problem that is currently prevalent, is that in most jurisdiction in the United States only certain people can enter a marriage contract. One party has to be a man and the other a women and neither can be married to a different person. This is not acceptable under libertarian theory. Libertarians hold the position that government should not define marriage, issue a license, or impose the terms and conditions of marriage. All of this should be left up to the individuals who enter the relationship.
The Uniform Commercial Code (UCC) also acts in a somewhat similar way in imposing terms of contract whether the parties have actually accepted them or not. The UCC imposes default terms to certain types of contracts whether the parties have agreed to them or not. The parties can opt out of some of these provisions, but if they do not opt out, then the terms apply. This also seems to be inconsistent with libertarianism because the terms are imposed on the parties.
Committing a crime can change you legal status. Entering a partnership or other business relationship can change your legal status. For example, if you enter a partnership, your partner’s actions can make you liable for your partner’s actions that are related to the business.
So, as long as your actions are voluntary, having your legal status change is consistent with libertarianism.